Lithium Battery Charging System

Thank you guys for the replies. I went with the Interstate SRM31 battery. We're thinking of getting a fifth wheel here in the not too distant future (and of course keep the Lance). If we do that, I will go the Lithium route with fifth wheel. I need a whole lot of YouTube time before I consider tackling a job like this. Safe camping.

greenno wrote:
I ended up building my own LifePO4 set-up myself.
Went from 98ahr's to 560ahr's.
Already had 510w of solar on roof and a 30a charge controller that was compatible. Changed out my 120v on-board charger ( have yet to even use ). Also added a Victron DC/DC 18a isolated charger to top off when driving down the road and never have to worry.
Also added a 3000w inverter that we use for the coffee maker in the AM and occasional microwave use and haven't used my generator since going this route.
Probably set me back 2.5k total but should last quite a while.
With the storage capacity I have now I don't even charge everyday.



Not a cheap way to go but I know it will last and it's installed correctly.
Retired IBEW Contractor here in SD so I gots the skills.
Good luck.

Sounds like a very sweet set-up you’ve got Sir :) !!

(FWIW, very similar to my 400a/h LFP supported by 660w rooftop truck camper solar…)

3 tons

I ended up building my own LifePO4 set-up myself.
Went from 98ahr's to 560ahr's.
Already had 510w of solar on roof and a 30a charge controller that was compatible. Changed out my 120v on-board charger ( have yet to even use ). Also added a Victron DC/DC 18a isolated charger to top off when driving down the road and never have to worry.
Also added a 3000w inverter that we use for the coffee maker in the AM and occasional microwave use and haven't used my generator since going this route.
Probably set me back 2.5k total but should last quite a while.
With the storage capacity I have now I don't even charge everyday.



Not a cheap way to go but I know it will last and it's installed correctly.
Retired IBEW Contractor here in SD so I gots the skills.
Good luck.

"I don't do a lot of boondocking, but that could always change in the future."

I boondocked with wet batteries and now with a Lithium battery. With an adequate solar system recharging either type of battery is not an issue. Sure, my Lithium has more usable power and it recharges faster but those are the only differences I've noticed.

The existing setup should work perfectly well. Just drop in the battery and have fun. Consider 200 to 400 watts solar if getting off grid much.

CYCLEPATH wrote:
Will the truck alternator charge the Lithium battery? Will the current battery separator need to be changed? It seems a lot easier to just install a new Interstate. I don't do a lot of boondocking, but that could always change in the future. Thank you.

The short answer is, if your current lead acid meets your needs, stick with it. Maybe upgrade to a pair of 6V golf cart batteries.

Your current battery separator would have to be replaced with a DC-DC charger. It prevent discharging the vehicle battery and ensure that you LiFePO4 battery is charged correctly.

Nothing wrong with wet cell batteries, especially if you want to keep it simple, not have to worry about anything. The technology to recycle them is there too.

The prior lithium hazard was associated with a ‘hotter’ more power dense chemistry using cobalt… A common ‘drop-in’ type RV battery (straight replacement) is of a friendlier, safer chemistry (LiFePO4, or ‘LFP’ = Lithium, iron, phosphate..) and there’s virtually no record of such mishaps with this chemistry and can be shipped as non-hazardous…Also, the built-in BMS System (Battery maintenance system) works as a redundant secondary catastrophic safeguard that prevents over current, overcharge (etc…), and acts to balance the cells upon a full recharge (although with LFP a ‘full recharge’ that enables cell balancing should be viewed more as a periodic rather than a routine regime)..

Your PD with charge wizard will work fine so long as you kick it into the Absorption or Boost Mode (14.4v), but once fully charged (i.e. post cell-balancing) discontinue charging shortly thereafter since it’s not good to continue charging for extended periods, and for this same reason (unlike wet-cell types) LFP’s should not be equalized (over time can lead to damaging dendrite formation)…

Determining ‘accurate’ LFP State of Charge (SOC) will require a decent LFP compatible meter (or say bluetooth), such as a Victron ‘Smart Shunt’ or BMV-712 (or equiv), this due to LFP’s relatively flat discharge voltage plateau…With either battery type a good shunt based meter (shunt installed in batt neg cable) is truly an invaluable asset!!

Usable wet-cell depth of discharge (DOD) is down to about 50’ish percent, whereas LFP’s can routinely go down much deeper discharge, some even advertised to zero percent, but in the interest of cycle longevity a somewhat lesser DOD would seem more practical…

In summary, LFP’s have a relatively flat, stable voltage plateau, uber deep DOD (Depth of Discharge), a FULL daily charge is not a routine objective (unlike FWC, something best avoided except for occasional re-balancing), single stage charging is ideal (tolerant to a relatively wide breadth of ‘Absorption’ or ‘Boost’ voltages (upper 13’s not to exceed 14.6v), tolerant to extended Float mode (at less than 13.6v,) tolerant towards infrequent charging or ‘less than full’ charging cycles for a near grid-like experience, and efficient harvest receptivity to more rapidly exploit peak harvest hours…

On the downside, LFP’s cannot be charged below 32d/F, but can continue to be discharged to as low as -4d/F…Since they don’t off-gas one option may be to interior mount (or heated basement), while higher-end versions can be had with built-in heaters, or one might insulate battery case with a electric (12 or 120v) battery blanket…Due to LFP’s uber deep DOD ability, charging can often be postponed until the arrival of warmer ambient temps..

3 tons