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danbar
Samba Member
Joined: October 16, 2011
Posts: 464
Location: North Bend, WA
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 Posted: Wed Jun 07, 2023 9:52 pm Post subject: LiFePo4, Do I need a DC to DC charger? |
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I need a new house battery and I’m running it under the drivers seat. Currently I have a 65ah AGM but it’s just a hair too tall and I’m looking for something that will fit under the cover. I also have a Blue Sea ACR and a NOCO Genius shore power charger. I want to keep things simple right now so can I just drop a gowesty Lithium battery in with the setup I have or would I also need to add a DC to DC charger as well? For the record I do not have the time or bandwidth to deal with a more complicated solution right now. My power needs are modest, lights, water pump and charging my phone for a long weekend.
So is anyone running a LiFePo4 and charging it with the alternator and/or shorepower?
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'88 SCA High/Pop-top Syncro camper
'61 Meyers Manx |
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zimflux
Samba Member
Joined: September 30, 2015
Posts: 192
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| Posted: Thu Jun 08, 2023 3:14 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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Yes you do in order to properly charge your new lithium battery. Lithium batteries have different charge requirements than lead acid. ACR cannot be used.
This is a very common question and there are lots of write-ups here and all over the web.
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17155
Location: Retired South Florida
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| Posted: Thu Jun 08, 2023 4:47 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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I was in the same boat. Read a lot of information and watched quite a few you tube videos of a guy who evaluates lithium batteries. I’ll look later for his channel if you want.
The consensus was a dc to dc charger was ideal. I decided on the Renogy 20 amp model. Purchased through Amazon. I added a toggle so I can manually control it when needed. I don’t always need it running. 20 amps doesn’t require big cables which simplified the install.
I have no need for solar yet. We are moving almost every day when we travel. Use between 8 and 15 amps a night camping.
The battery I purchased was based on reviews, price, size, and features. It’s 100 amp and does not fit under the drivers seat. My AGM was under the rear seat already. It has 2 features. A built in heater that’s automatic and a BMS with blue tooth. I installed an app that gives me so much information I did not have before. I use it daily. I can see the SOC state of charge. Real time amps in or out and battery temp to name a few. It is also counting uses.
Good luck sorting through the info. Well worth the investment. This is my 3rd iteration of a coach battery system.
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dobryan
Samba Member
Joined: March 24, 2006
Posts: 16508
Location: Brookeville, MD
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| Posted: Thu Jun 08, 2023 5:32 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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If your power needs can be met solely by the battery for one weekend of camping then you can just use the NOCO Genius shore charger (assuming it has a LiFePO4 setting) to recharge the battery when you get home.
Basically you will have no on board charger attached to your alternator for charging on the road, just with 110V at home or elsewhere.
This is a simple as it gets and several members here have done it that way since it met their specific needs. YMMV.
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Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD
"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson
MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646
Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371
The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794 |
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jimf909 
Samba Member
Joined: April 03, 2014
Posts: 7480
Location: WA/ID
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| Posted: Thu Jun 08, 2023 6:10 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| danbar wrote: |
So is anyone running a LiFePo4 and charging it with the alternator and/or shorepower? |
If the GW battery will supply your electrical needs for a long weekend, Dave's suggestion to charge only from a shore charger is the simplest solution. You'll just need to do some math to see if the battery will meet your needs w/out being recharged or go without aux electric at the end of the weekend.
To charge from the alternator w/out a DC-to-DC charger 1) puts the alternator at risk of very heavy uncontrolled loads being pulled by the LiFePo battery (when the battery is low) and 2) puts the battery's BMS at risk of constantly shutting down charging because the alternator is trying to charge overcharge the battery (when the battery is full).
I tried to talk myself out of a DC-to-DC charger for weeks but decided that using one was best for my situation.
_________________
- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro).
Last edited by jimf909 on Thu Jun 08, 2023 6:11 am; edited 1 time in total |
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dabaron
Samba Member
Joined: June 21, 2018
Posts: 2562
Location: Philly, mang
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| Posted: Thu Jun 08, 2023 6:10 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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i have a 150aH LiFePo4 and use a Renogy DC to DC charger which also has an MPPT solar charge controller built in. i have not hooked up a solar panel to it yet as driving around for an hour gives me a day's worth of charge. i can go almost 3 full days without recharging starting with a full battery.
_________________
1991 Vanagon GL Camper
i had no idea i wanted to be a mechanic
"burnin oil and cookin coils" -- Destructo
BiWerks Design, LLC
Last edited by dabaron on Thu Jun 08, 2023 6:16 am; edited 1 time in total |
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danbar
Samba Member
Joined: October 16, 2011
Posts: 464
Location: North Bend, WA
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| Posted: Thu Jun 08, 2023 6:16 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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Damn, I was really hoping this wasn’t the case. Given that I need a house battery for a trip next weekend and don’t have time to upgrade the electronics right now, does anyone have advice on an AGM battery that fits under the front seat? I stopped by Mule last week and talked to them and they were unable to find anything from their suppliers that would fit in the available space.
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'88 SCA High/Pop-top Syncro camper
'61 Meyers Manx |
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dabaron
Samba Member
Joined: June 21, 2018
Posts: 2562
Location: Philly, mang
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| Posted: Thu Jun 08, 2023 6:19 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| danbar wrote: |
| Damn, I was really hoping this wasn’t the case. Given that I need a house battery for a trip next weekend and don’t have time to upgrade the electronics right now, does anyone have advice on an AGM battery that fits under the front seat? I stopped by Mule last week and talked to them and they were unable to find anything from their suppliers that would fit in the available space. |
https://www.amazon.com/BLUETTI-Portable-EB3A-Recharge-Generator/dp/B09WW3CTF4
connect this to fuse #3 and it will power the lights, radio, and you can charge your phone...
_________________
1991 Vanagon GL Camper
i had no idea i wanted to be a mechanic
"burnin oil and cookin coils" -- Destructo
BiWerks Design, LLC |
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dobryan
Samba Member
Joined: March 24, 2006
Posts: 16508
Location: Brookeville, MD
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| Posted: Thu Jun 08, 2023 6:55 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| danbar wrote: |
| Damn, I was really hoping this wasn’t the case. Given that I need a house battery for a trip next weekend and don’t have time to upgrade the electronics right now, does anyone have advice on an AGM battery that fits under the front seat? I stopped by Mule last week and talked to them and they were unable to find anything from their suppliers that would fit in the available space. |
So the LiFePO4 battery you had in mind will not last the weekend?
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD
"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson
MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646
Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371
The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794 |
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danbar
Samba Member
Joined: October 16, 2011
Posts: 464
Location: North Bend, WA
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| Posted: Thu Jun 08, 2023 7:02 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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I’m sure it would but I would really prefer something that can charge off the alternator for longer trips where there is driving between stops involved. I don’t typically camp at places with shore power available.
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'61 Meyers Manx |
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dobryan
Samba Member
Joined: March 24, 2006
Posts: 16508
Location: Brookeville, MD
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| Posted: Thu Jun 08, 2023 7:06 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| danbar wrote: |
| I’m sure it would but I would really prefer something that can charge off the alternator for longer trips where there is driving between stops involved. I don’t typically camp at places with shore power available. |
In your shoes I would buy the LiFePO4 and install it for your weekend trip without any charger from the alternator.
Then buy a DC/DC charger and install it. The DC/DC charger is drop dead simple to install. It just goes in line between the alternator and the battery. You already have the wiring there so it should be simple. Just swap out the ACR. Do check that the wire gauge is adequate for the charger, you can comment on that here and folks will let you know.
Otherwise you are throwing money at a new battery that will really not meet your long term goals.
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD
"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson
MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646
Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371
The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794 |
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jimf909
Samba Member
Joined: April 03, 2014
Posts: 7480
Location: WA/ID
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| Posted: Thu Jun 08, 2023 7:18 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| dobryan wrote: |
| danbar wrote: |
| I’m sure it would but I would really prefer something that can charge off the alternator for longer trips where there is driving between stops involved. I don’t typically camp at places with shore power available. |
In your shoes I would buy the LiFePO4 and install it for your weekend trip without any charger from the alternator.
Then buy a DC/DC charger and install it. The DC/DC charger is drop dead simple to install. It just goes in line between the alternator and the battery. You already have the wiring there so it should be simple. Just swap out the ACR. Do check that the wire gauge is adequate for the charger, you can comment on that here and folks will let you know.
Otherwise you are throwing money at a new battery that will really not meet your long term goals. |
^^^This. Buying an AGM for the short-term is buying old tech that just plain isn't as good as LiFePo. LiFePo + the DC charger will last several thousand cycles, i.e. the last aux battery you'll buy until your needs change.
If you really want an AGM battery, the Interstate Battery store in Southcenter may have one that fits in stock. I bought many lead acid batteries from them:
https://www.interstatebatteries.com/locations/all-...ntent=9128
_________________
- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
|
Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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Sodo
Samba Member
Joined: July 06, 2007
Posts: 9620
Location: Western WA
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| Posted: Thu Jun 08, 2023 7:25 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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I just installed the Renogy DCC50S + MPPT. (it's called a "50Amp" charger)
I have a 150AH LiFePO4 system under the driver seat.
I'm currently "pleased" with the charger's operation but I was surprised that it's max alternator charge is 25A. I had heard it before but thought it was "old news" plus got all excited at the $229 sale price.
Renogy obscures this important detail - they don't state these numbers outright.
But what's nice is it also trickle charges the starter battery via Solar, covering my losses (USB ports and forgetfulness).
(I have 100W or ~7A solar)
Anyway it looks like the max charge I can get with 100W solar is 25+7=32A.
32A ain't bad!
One thing to remember is that a Lithium battery charges fast, ALWAYS.
Whereas a lead battery might refuse the charge, taking much longer to top off.
I remember driving, driving, driving, hoping the lead battery would agree to take the amps available.
It often refused, just taking a sip.
I also had a 30A IOTA house charger - that I deleted from the van.
I never used it, and don't envision ever needing it with the solar and alt charging on-board.
======
If no solar and an electric fridge - I'd recommend getting 100Ah of Lithium.
I would never buy another LEAD house battery.
I don't camp often enough in sub-zero to subject myself to lead again.
And if I ever do, I'll add a battery heater.
Maybe check with DAKOTA Lithium, they are in the SODO  area of Seattle.
_________________
'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
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kamzcab86
Samba Moderator
Joined: July 26, 2008
Posts: 7925
Location: Arizona
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| Posted: Thu Jun 08, 2023 8:37 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| danbar wrote: |
| Damn, I was really hoping this wasn’t the case. Given that I need a house battery for a trip next weekend and don’t have time to upgrade the electronics right now, does anyone have advice on an AGM battery that fits under the front seat? I stopped by Mule last week and talked to them and they were unable to find anything from their suppliers that would fit in the available space. |
I've been using this: https://gmienergy.com/SLR50 (I've bought it on Amazon, but it's currently unavailable through them).
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~Kamz 
1986 Cabriolet: www.Cabby-Info.com
 1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子 |
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dabaron
Samba Member
Joined: June 21, 2018
Posts: 2562
Location: Philly, mang
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| Posted: Thu Jun 08, 2023 8:55 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| Sodo wrote: |
I just installed the Renogy DCC50S + MPPT. (it's called a "50Amp" charger)
I have a 150AH LiFePO4 system under the driver seat.
I'm currently "pleased" with the charger's operation but I was surprised that it's max alternator charge is 25A. |
i get well into the 40A+ charge current based on what the Overkill BMS reads. i just ran out and at idle am getting 29A and when i rev the engine above 2000 rpm it jumped to 36A.
what BMS are you using, what is the charge current rating?
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1991 Vanagon GL Camper
i had no idea i wanted to be a mechanic
"burnin oil and cookin coils" -- Destructo
BiWerks Design, LLC |
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1988M5
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Joined: January 23, 2016
Posts: 674
Location: Santa Cruz, CA
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Sodo
Samba Member
Joined: July 06, 2007
Posts: 9620
Location: Western WA
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| Posted: Thu Jun 08, 2023 10:39 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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| dabaron wrote: |
| Sodo wrote: |
I just installed the Renogy DCC50S + MPPT. (it's called a "50Amp" charger)
I have a 150AH LiFePO4 system under the driver seat.
I'm currently "pleased" with the charger's operation but I was surprised that it's max alternator charge is 25A. |
i get well into the 40A+ charge current based on what the Overkill BMS reads. i just ran out and at idle am getting 29A and when i rev the engine above 2000 rpm it jumped to 36A.
what BMS are you using, what is the charge current rating? |
OK it's a new install and I don't have test info because the LiFePO4 is full.
Thanks for that in-use data, I'll look at what the (Overkill) BMS says and report back.
After the battery gets 'hungry' I can report charge info.
It would be great if I can get 50A from the alternator when I need it.
Or 43A from the alt and 7A from Solar - that's perfect too..
I was "reading between the lines" combining the obscure statements Renogy makes in their printed owners manual.
That's one thing about Renogy, it "looks kinda USA", USA photos etc the manuals look good but it's not a USA company. $229 was good though, if it's gonna work.
Renogy could be Thailand, which (moving forward....?) may be a better place to buy than China.
_________________
'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 17155
Location: Retired South Florida
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| Posted: Thu Jun 08, 2023 10:59 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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My Renogy 20 amp DC to DC charger purchased from Amazon for around $100 will output 20 amps when the BMS will accept it. Idle or going down the road. The Renogy output doesn’t seem to care about what the alternator is doing.
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dobryan
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1988M5
Samba Member
Joined: January 23, 2016
Posts: 674
Location: Santa Cruz, CA
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| Posted: Thu Jun 08, 2023 11:33 am Post subject: Re: LiFePo4, Do I need a DC to DC charger? |
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50 amps is a lot to ask the alternator to give at idle. If the Lithium battery was at a low SOC (state of charge), it would try to consume a zillion amps. A dc-dc converter not only gives the proper voltage, but it also regulates the max current (amps), the selection of a lower powered unit will be nice to the cars system. If you’re already invested in a 50 amp version, I suggest adding a switch to allow it to work only when traveling down the road at higher than idle RPM.
Food for thought/fear, https://youtu.be/jgoIocPgOug
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1991 tin top GL
2002 Winnebago Vista. VW VR6 24V Eurovan front clip powered class C 21' RV.
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