Isolator and Lithium Battery

[Captian K]

With my electrical setup, I have installed a Battery Dr battery isolator to go from my alternator to my two Battleborn Lithium batteries. I have never been able to get the unit to work. I called Wirthco and they told me that their isolator is not made for Lithium batteries.


1. has anyone else heard that
2. if you have lithium batteries, what isolator are you using.


Thanks,

[ShuttlePilot]

Greetings Captain K,

I'm not familiar with the Dr Battery isolator so I'm not sure why it wouldn't work for you. I'm also confused about the use of an isolator for a lithium battery setup.

I can answer the second half of your question though. Last winter I also improved my house battery to a pair of BattleBorn batteries. I opted for the Sterling Battery to Battery charger 60amp. I chose the Sterling because it's small and extremely configurable to provide the charging algorithm BattleBorn specifies. This setup has been working really well over the last year, however I'm not sure I'd recommend the Sterling as it has some significant short comings IMO. I keep intending to do a post of this change to lithium project, just seems like everyone is doing lithium these days and posting on the internet about it. In all the internet posts, it seems most people go two routs with lithium charging, Battery to Battery charger or dedicated second alternator. Anyway, Here are some pictures for entertainment.


Greg (Scaff77), your thoughts on the Dr Battery Isolator?

- Eric

[simplesez]

We just went with the Sterling to replace the Battle Born lithium battery isolator which did not work with the smart alternator in our 2020 Transit.

It will not charge as quickly but can handle the smart alternator (regenerative) that Ford is now using. We did lose the momentary switch also.

[ShuttlePilot]

Question for simplesez, and apologies to Captain K for the side conversation, but it is related.

I haven't been able to ask another Sterling B2B owner yet but my unit rapidly reaches the thermal limit of the heat sink and goes into the half power mode, cycling between full and half power. It appears the thermal limit of the FETs it set to 185*F which triggers the half power mode. Once cooled to 170*F it goes back to full power mode. This duty cycle, depending on cabin temp, can be as often as 60/40. As you can see in my photo my Sterling is in a pretty confined space but there are cooling fans on the cabinet to evacuate the heat of the unit. It seems the engineers of the Sterling greatly underestimated the needed heat dissipation to maintain the 60 amp input/45 amp output 100% of the time. You mentioned the lower output of the Sterling which was somewhat true of mine. Just wondering if I have a bum unit or is all of these like this.

And just for fun I hot rodded the cooling on mine to lengthen the full power duty cycle.

- Eric


Fans are removed at the time of photo.

[simplesez]

We haven't installed it yet but can let you know next week. Good info on the cooling.

[Scalf77]

Captain K
I am not really sure why it doesn't work with lithium, they do say all over there website that it only supports lead acid batteries. Was it throwing current faults or any error codes. It is possible the difference in resting voltages between the two chemistries may have some effect.

Generally you do not want to go with a direct ACR or Smart Relay device when charging a lithium battery from an alternator. You run the risk of overcharging the lithium battery or possibly damaging your alternator.

I believe the one unit Simplesez was talking about is the Li-BIM. This unit is programmed for the Lithium batteries, to protect both the alternator and battery.

Part of the problem with Lithium is there thirst for current compared to like size lead acid. They will generally ask for more current from the alternator then a lead acid battery. While the alternator can only put out what it is designed for, there can be a problem at low speeds or idle. The current output can be higher than the cooling provided at that RPM. There were a lot of early reports of alternators burning up when directly attached to a lithium battery bank.

Eric,

I search through lots of data on the Sterling site, but could not find what their operating temperature is, I expect it is there but I just didn't see it. 185°F is pretty standard temp limit, so then it just comes down to cooling the heat sinks, obviously more fan could help to a point. What altitude are you? As that will have an impact on fan performance.

greg

[ShuttlePilot]

Greg,

I live at 6200' and am often higher than that. I follow you on the altitude is a factor as we battle reduced radiator, intercooler, oil cooler performance at altitude a lot. However on this I don't think the difference would be noticeable outside of controlled conditions. For reference, if it is cold in the van, below 40*F, the unit will maintain a heat sink temp of around 170*F and not derate to 30amps. Anything above that and it will reach the 185 and start to cycle, frequency dependent of ambient temps.

Here are my thoughts. I'm not complaining. The little unit dose the job, and even though I have criticisms for improvement, it checks most of the boxes of my wants in this project. I haven't been able to compare my unit to another to see if there is a difference. Some back of the envelope math has me thinking the unit is 75% efficient. Not thermally limited performance is a steady 60 amps in 45 amps out. I'm thinking it needs to dissipate around 250 watts from the heat sinks with fans. Based on the size of the heat sinks with 40mm fans trying to dissipate 250 watts seems like it's asking a lot.

I don't remember if I read that current is limited at 185*F or I just observed it from the remote panel. I might of just accepted it as you say 185 is pretty common. It doesn't seem to stress with this duty cycle, and may be intended to run as such, but I would prefer it have more of the full throttle is 80% of it's thermal capacity approach. It should also be noted for anyone purchasing that this is not a 60 amp out to your battery unit, it consumes 60 from the source and delivers, when full capacity, 45 amps out to the charged battery. So really the delivered current capacity, at max heat sink temps, is a duty cycle between 45Amps and 30Amps. When doing the math that isn't all that much lost watt hours of charge as long as the duty cycle isn't to long. Note, the unit can be set to the 30amp output continuously which I have observed eliminates all heat issues and is capable of 100% duty cycle at 30Amps output.

Anyway, I feel I have hijacked Captain K's post. If this is a conversation we would like to continue I'll start a thread on my build and we can get as deep as we want over there.

- Eric

[jonyjoe101]

have you tried your battery doctor isolator with a lead acid to see if it works? maybe the battery doctor is bad or your alternator isn't putting out enough volts after it starts. For the isolator to activate the start battery voltage has to be 13.4 volts or higher.

Lifepo4 battleborn charges to 14.4 volts just like a lead acid, so it should work (the bms on the lifepo4 wont trip/activate until 14.6 volts which it will probably not reach with the alternator). As per battleborn its suppose to be a drop-in replacement for a lead acid.
According to the battery doctor manual, the isolator will connect both batteries together when the start battery voltage is above 13.4 volts(engine running) and the aux battery voltage is at least above 3 volts, and it will disconnect the batteries if the star battery voltage drops below 12.8 volts for more the 1 minute.

In the battery doctor website I didnt see anything that said lifepo4 cannot be used. All I saw was a note about "Batteries of differing voltages cannot be used.".

Lead acid 12.8 volts and lifepo4 13.1 volts are about the same voltage. I connected lead acid and lifepo4 and left them connected all night long, they equalize at 13.1 volts. So paralleling a lifepo4 and a lead acid is possible without any problems.

[Captian K]

Thanks for all your help. I did get a hold o someone at battery doctor and they did tell me that lithium batteries have a different algorithm than standard batteries. he said it is pointed out in the instruction manual that the unit will not work with lithium.


I thought that was odd.


I called Battleborn batteries and they said the same thing. for lithium batteries, you have to have a different battery isolator. learned something new.


if you would like to know more. go to battleborn website and in the search, type in "BIM". the product should come up. it looks like a green funny Christmas tree.


I will be ordering one in a few days and I will let you all know.

[Captian K]

Originally Posted by ShuttlePilot

Greetings Captain K,

I'm not familiar with the Dr Battery isolator so I'm not sure why it wouldn't work for you. I'm also confused about the use of an isolator for a lithium battery setup.

I can answer the second half of your question though. Last winter I also improved my house battery to a pair of BattleBorn batteries. I opted for the Sterling Battery to Battery charger 60amp. I chose the Sterling because it's small and extremely configurable to provide the charging algorithm BattleBorn specifies. This setup has been working really well over the last year, however I'm not sure I'd recommend the Sterling as it has some significant short comings IMO. I keep intending to do a post of this change to lithium project, just seems like everyone is doing lithium these days and posting on the internet about it. In all the internet posts, it seems most people go two routs with lithium charging, Battery to Battery charger or dedicated second alternator. Anyway, Here are some pictures for entertainment.


Greg (Scaff77), your thoughts on the Dr Battery Isolator?

- Eric

Thanks Eric for the reply. Battery Doctor is a name of the battery isolator by a certain company. it is used as a connection piece to go from your starting battery to your house battery. it allows currect to flow in one direction while charging your battery when the vehicle is moving.


for you charger system. I have a Samlex inverter / charger. I decided to go with an all in one unit. this is my inverter, charger and sure power transfer switch unit. I have been happy.