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How to trickle charge FLA starter battery from LiFePO4 house battery?

Touring

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I’m part upgrading a 12 year old Sprinter LWB camper. I’ll retain the main management/wiring system. This provides shore charging of house or starter batteries but not both together. Additionally a PV panel charges through a single output PWM to the house bank. I want my starter battery to charge when off grid. A simple fix would be a trickle charge from a 12V stand by charger wired between house and starter battery.

However, I’ll be replacing the FLA house batteries with LifePO4. I’m told that a charger like this will only work FLA to FLA. Example: Votronic 12V StandBy charger. I could fit a dual output solar controller, but prefer Victron build and 5 year warranty. Victron solar controllers don’t have dual output.

As mentioned, I won’t be stripping out an old van and intend selective upgrades as follows:
Victron Superpack 12.8V LifePO4 100Ah x 3
PV panels: 100watt x 3
Victron BlueSolar MPPT 100V/30A
Sterling B2B Pro Batt Ultra 12V DC/DC 60amp
Victron BMV-700

What is the best way to charge my FLA starter battery? With that sorted, I think I’m ready for ordering the bits and having it wired up. I’m no expert, so if anyone sees errors or improvements please let me know.
 
I installed a Trikl Start in 2011 and its kept my starter battery good, even now.
I switched my house batteries to LiFePO4 about 4 months ago and it seems to be doing just fine. Not sure why the Trikl Start would care what my house battery is.

Here is the guide i followed. Pretty easy once you get the passenger seat pulled. I have not seen this unit since 2011.

 
Thanks for your answer.

I can't find the Trik-L-Start either, though it appears to be pretty much the same as the Votronic unit detailed in my question. Like you, I'm wondering - if these trickle charge units give energy to the start battery, which is an unchanged FLA, why it would care what the house battery is - whether FLA or LiFePO4. Does anyone know? I don't want to take any chances with expensive new LFP batteries. Votronic state that their trickle charger is only for FLA to FLA.

A trickle charge from the house battery to the starter battery seems ideal, if there is a unit available that monitors SOC and keeps both batteries at optimum, even when the chemistry between them is different. Does something like this exist?
 
This is interesting. When my RV is just sitting in the driveway, i have the solar turned off and leave the batteries at a storage voltage below
13.35 so this would NOT keep the engine battery charged for me.
The NORMAL setting is best for my use. (Someone correct me if i am missing something!)
>>>
The "LITHIUM" mode changes the turn-on and turn-off voltages to 13.45 and 13.35 volts, respectively.

Removing the jumper instantly restores the "NORMAL" 13.2/12.8 volt turn-on/turn-off settings.
 
Looking at the tech info on the new model - AMP-L-Start - answers the question why a trickle charger would care what the house battery is. The turn on/turn off voltages are important, and the Votronic that I was considering doesn't have the necessary jumpers.

I thought you had the Trik-L-Start ? Does that have voltage adjusting jumpers? Or have you now fitted the later AMP-L-Start?
 
I've got a Silicon Diode between my house battery and my starter battery. With a Voltage drop of 0.7V

So that means, every time my house battery has a Voltage of 0.7V more then the starter battery, it also charges this one.

For instance, my house battery charges up to 14.4V - 0.7V = 13.5V would trickle charge my starter battery to a nice voltage
Works perfect for almost 5 years now.

Invest was like $1 or two $2 for a 20A Diode and two 20A fuses on both sides.

The only downside with this contraption is that if you got a parasitic draw on the engine battery, it would also empty out your house battery over time.

If you your lithium battery would charge to a even higher voltage you could put Diodes in series - so you would end up with a Voltage drop of 1.4V
Lead batteries are simple, as long as they are sitting somewhere between 13.2 and 13.5V they are happy to eternity.
 
I thought you had the Trik-L-Start ? Does that have voltage adjusting jumpers?
As i said, i have the Trikl Start. No jumpers that i know of. Its been buried for nearly a decade.
I find that its charging parameters work well with my LiFePO4 house battery strategy: remain between 13 and 13.8v. I like storing them at 13-13.12v. (Sitting in driveway with solar panels disconnected, house batteries at 13.1v).
Looks perfect to me. Starting battery will be 10 years old on jan 7th 2021.
 
I am interested in something like this for my 24V house to 12V starter battery.
I am sure I could use a Victron Orion DC-DC charger. Probably a more expensive than I would like.
 
The nonisolated 24/12-20 is only $65.


That is cheaper than the products you guys are talking about and no question about configuability or quality.
 
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That is cheaper than the products you guys are talking about and no question about configuability or quality.
Yea, i too am a Victron fanboy so if this ever dies or when i get a new RV, the Orion will get a good looking over.
I REALLY cannot complain about this Trikl Start though, its done the impossible as far as i a concerned - who ever heard of an engine battery staying alive for coming up on 10 years?

(this of course means that the next time i start the sprinter, the starting battery will be dead...)
 
Yea, i too am a Victron fanboy so if this ever dies or when i get a new RV, the Orion will get a good looking over.
I REALLY cannot complain about this Trikl Start though, its done the impossible as far as i a concerned - who ever heard of an engine battery staying alive for coming up on 10 years?

(this of course means that the next time i start the sprinter, the starting battery will be dead...)
The starter batteries in my E350 van where 6 years old and still good when I bought it. Amazing, batteries rarely live past 3 years in Phoenix.

I replaced them.
 
who ever heard of an engine battery staying alive for coming up on 10 years?

Had multiple of those, usually gasoline engines when the battery is somewhere in the interior of the car and not in the engine compartment.
 
Had multiple of those, usually gasoline engines when the battery is somewhere in the interior of the car and not in the engine compartment.
Phoenix heat eats batteries. Although the van batteries are underneath, not in the engine compartment so there could definitely be something to what you say.
 
Lead melts a low point, around 600F a Engine compartment routinely gets around 200F, where the already soft lead get's even softer.
My BMW and Volvos had their batteries under the Trunk and they routinely got 10+ years old.

Diesel Engines eat starter batteries for Breakfast. Rarely had on in cold Germany last more then 4 years.
 
Sprinter battery under floor inside cab so thats probably been a big part of its longevity. I thought it was an odd place but now i see one reason to have it there.
 
Sprinter battery under floor inside cab so thats probably been a big part of its longevity. I thought it was an odd place but now i see one reason to have it there.
Me too. Changing the batteries in my van was a pain in the rear, but not having to do it every 3 years is a huge advantage.

I see that this was totally driven by a lack of room in the engine compartment, but i will take any advantage I can get.
 
The nonisolated 24/12-20 is only $65.


That is cheaper than the products you guys are talking about and no question about configuability or quality.

Hope this is on topic. I've been looking for something similar. I would like to charge dual 48v lifepo4 battery banks. When primary #1 is full it would switch to Battery #2 and charge it. #1 primary for heavy loads air conditioner and fridge and #2 for lights, tv , radio etc.
 
Hope this is on topic. I've been looking for something similar. I would like to charge dual 48v lifepo4 battery banks. When primary #1 is full it would switch to Battery #2 and charge it. #1 primary for heavy loads air conditioner and fridge and #2 for lights, tv , radio etc.
What is your charge source? Sounds like you are going to need some intelligence to do this.

This thread discusses combining two dissimilar 48V batteries.

 
Source would be 5- 400w pv panels, Growatt 3000 48v all in one inverter battery#1 48v 280ah and #2 battery 48v 100ah.
 
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