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Cpetry7
Samba Member
Joined: March 16, 2021
Posts: 4
Location: Summerfield, Florida
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 Posted: Thu Dec 12, 2024 2:33 pm Post subject: LiFePO4 house battery with no dc-dc charger |
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Completely recognizing my previous mistake of purchasing and installing a 100ah LiFePO4 house battery in my 85 westy without fully understanding the need for a dc-dc charger to support it.i am now temporarily stuck with this battery being charged directly by the alternator with the gowesty aux battery setup while I try to set aside some funds/time to get a dc-dc charger into my system.
My question is - are there major risks to me driving the van in its current state? Do I risk just stranding myself due to the alternator being over loaded and going bad?
Appreciate the help! |
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shagginwagon83 
Samba Member
Joined: February 07, 2016
Posts: 4331
Location: SWVA
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| Posted: Thu Dec 12, 2024 2:38 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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You're probably okay for now. What LiFePO4 battery did you purchase? Hopefully, it has an internal temperature sensor to prevent charging below freezing.
Just keep in mind that the battery will likely only charge up to about 90% of its maximum capacity in this setup.
_________________
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram: @joannthevan |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 18758
Location: Retired South Florida
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| Posted: Thu Dec 12, 2024 2:44 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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| My understanding is the dc to dc charger provides stable amps and volts from a varying source. I purchased a Renogy 20 amp from Amazon for around $100. Very happy with it. Seems to keep up with our current use. |
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shagginwagon83
Samba Member
Joined: February 07, 2016
Posts: 4331
Location: SWVA
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| Posted: Thu Dec 12, 2024 3:02 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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Some DC-DC chargers (like Redarc) have internal temperature sensors and will disable charging in extreme temperatures.
_________________
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram: @joannthevan |
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bobbyblack
Samba Member
Joined: May 21, 2015
Posts: 4619
Location: United States, Iowa
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| Posted: Fri Dec 13, 2024 9:18 am Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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So,
You might consider what you have in the engine compartment.. I assume that it is the stock 1.9 with a stock alternator. If so, you might consider trading out the voltage regulator. Don't go crazy (don't ask how I know), but there sure is a sweet spot that is a ways up from stock, can help all sorts of funk going on in these old beasts. Take a look at the 240turbo.com site for Voltage Regulators. Some say the fixed 14.8 Volt unit is to their liking, and others like the adjustable unit. Not all the much money, and you probably are looking at worn brushes in your present unit anyway.
https://www.prancingmoose.com/AdjustableVoltage.html
You might get closer to a full charge that way.
(See bottom of this post to read what a very smart and respected enthusiast and builder has to say)
| marcotheturbosteamengine wrote: |
| bobbyblack wrote: |
| OlRivrRat wrote: |
Bobby
What is the Voltage that You have found that these injectors are
Happiest with ??
ORR ~ DeanB |
14.9 at the Alterator after about 5 minutes since firing up the engine. I've got a couple other locations to look at voltage while underway, so at the dash with a few accessories running, I see a variety of volts. Oh, Cary a handful of spare fuses, as you're going to be replacing some. Just a little consequence I've run across. In my case, seems like the ones I've replaced are due to age. |
I do NOT recommend running A higher voltage regulator higher than 14.1v, any higher and you risk burning out components that were never designed to run at higher voltages. |
_________________
'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch |
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kamzcab86
Samba Moderator
Joined: July 26, 2008
Posts: 8459
Location: Arizona
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jimf909
Samba Member
Joined: April 03, 2014
Posts: 8168
Location: WA/ID
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| Posted: Fri Dec 13, 2024 10:58 am Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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| Cpetry7 wrote: |
My question is - are there major risks to me driving the van in its current state? Do I risk just stranding myself due to the alternator being over loaded and going bad?
Appreciate the help! |
First, the battery: if your alternator doesn't exceed 14.6 volts (3.65 max volts per cell x 4 = 14.6 volts) your LiFePO4 battery is safe. That's a one sentence summary of hundreds of pages of opinion and science. Edit: if your voltage regulator fails and the alt. starts passing 15, 16 or more volts which isn't unheard of, the battery and the van are no longer safe. More than 14.6 volts may damage the battery, more than 16 is risking battery failure, fire, great sadness, etc. (solution: a DC-DC charger).
As for the alternator, yes, the LiFePO4 is a hungry beast and will take everything and more that your alternator will give until it dies. The DC-DC charger is the solution in most cases. Until you install one I recommend a battery cutoff switch that allows you to cycle the charging by turning it off every 10 minutes* or completely. This needs to be sized to the current draw so the switch might cost about $30-$50.
* Disconnecting the battery form the alternator relates to duty-cycle. Devices that heat up when working are designed with a duty-cycle in mind. An air compressor is a good example where the manual may say that it's only expected to be reliable if running 20 minutes for every 60 and running it 60 minutes straight will lead to early death. Alternators are similar but the manuals aren't explicit. They're designed to operate the headlights and defroster fan continuously and to recharge a battery after a start for a short period of time but NOT to pump 50 amps into a LiFePO4 for 120 minutes. The cutoff switch allows you to cycle the charging to accommodate the alternator's duty cycle (this cycling is by the seat of your pants because we don't know the specs of your alternator's duty cycle but disconnecting the alt. for 10-20 minutes for every 10 minutes on is better than continuously running the alt. to charge the battery.).
Alternatively, disconnect the LiFePO4 from the alt. and only charge it with a shore charger or solar panels. In the end, the DC-DC charger is the simplest and best solution for most applications.
_________________
- Jim
| Butcher wrote: |
| This is the main fault with DIY'ers, they get together on these forums and pat themselves on their backs spreading bad information. |
Guilty as charged.
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 Fri Dec 13, 2024 12:43 pm; edited 2 times in total |
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dobryan
Samba Member
Joined: March 24, 2006
Posts: 17147
Location: Brookeville, MD
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 18758
Location: Retired South Florida
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| Posted: Fri Dec 13, 2024 12:57 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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| My point was for around $100 you can solve this with a Renogy 20 DC to DC charger. That is less than my prior Yandina and wouldn’t accomplish what you want to do. The 20 amp unit has reasonable wire gauge too. |
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jimf909
Samba Member
Joined: April 03, 2014
Posts: 8168
Location: WA/ID
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| Posted: Fri Dec 13, 2024 10:45 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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| MarkWard wrote: |
| My point was for around $100 you can solve this with a Renogy 20 DC to DC charger. That is less than my prior Yandina and wouldn’t accomplish what you want to do. The 20 amp unit has reasonable wire gauge too. |
Exactly. All the work arounds will cost time and money and will only be stopgaps until the best solution, the DC-DC charger, is installed.
_________________
- Jim
| Butcher wrote: |
| This is the main fault with DIY'ers, they get together on these forums and pat themselves on their backs spreading bad information. |
Guilty as charged.
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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vwhammer
Samba Member
Joined: May 20, 2006
Posts: 1010
Location: Boulder CO.
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| Posted: Sat Dec 14, 2024 3:51 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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Lifepo4 batteries have very low internal resistance and will take as much charge as is available.
Charging Lifepo4 from an alternator without a regulator (or DC to DC charger) with a proper current limit will kill an alternator very quickly.
Basically, it will simply try to pull more current than most alternators are rated for and cook it.
This can literally happen in less than a minute.
Lifepo4 also requires a specific charge profile that stock alternator regulators do not support.
This is hard on the batteries.
_________________
Pretty normal daily driver build
https://www.thesamba.com/vw/forum/viewtopic.php?t=708418&highlight=
4x4 build
https://www.expeditionportal.com/forum/threads/volkswagen-vanagon-4x4-conversion.162055/ |
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crazyvwvanman
Samba Member
Joined: January 28, 2008
Posts: 10374
Location: Orbiting San Diego
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| Posted: Tue Dec 17, 2024 10:00 am Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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Seeing this thread a few days ago caused me to check on current price and availability of the referenced 20 amp dc-dc units.
Seemed like the supply may be drying up.
Mark
| jimf909 wrote: |
| MarkWard wrote: |
| My point was for around $100 you can solve this with a Renogy 20 DC to DC charger. That is less than my prior Yandina and wouldn’t accomplish what you want to do. The 20 amp unit has reasonable wire gauge too. |
Exactly. All the work arounds will cost time and money and will only be stopgaps until the best solution, the DC-DC charger, is installed. |
Last edited by crazyvwvanman on Tue Dec 17, 2024 10:26 am; edited 1 time in total |
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shagginwagon83
Samba Member
Joined: February 07, 2016
Posts: 4331
Location: SWVA
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| Posted: Tue Dec 17, 2024 10:21 am Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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https://offgridstores.com/products/renogy-12v-20a-...8223497268
$96.99 on sale
Save 25% using SAVE25 promo code.
Free shipping
=== total is $76.61
_________________
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram: @joannthevan |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 18758
Location: Retired South Florida
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| Posted: Tue Dec 17, 2024 12:33 pm Post subject: Re: LiFePO4 house battery with no dc-dc charger |
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Brandon, that’s a good price. Thanks for sharing. A small 100 amp lithium battery along with a small DC to DC charger was a simple affordable way for a newbie/me to test the waters. This is my 3rd swing at a cabin battery with charging over 20 years. By far the best so far. Well worth it to me.
On a side note, the van was sitting outside under a cover last summer without being plugged in. The starting AGM battery was too discharged to crank. I have an AB battery switch from my second generation and was able to combine my 100 amp lithium for cranking. I expected the BMS to shutdown with the draw, but it worked fine. Way easier than connecting a jumper box or cables.
Your results may vary. Good time to snap up one of these in the link above. |
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1990 Vanagon Westfalia: 
