Adjustable battery isolator?

john61ct

Adventurer
BlueSea Systems CL-Series batteryLink ACR is current limited to 60A, intentionally so.

See also part no's 7635 and 7315
 

Rando

Explorer
Thanks for the suggestions!

The problem I am having is that I built a new lithium battery pack in my camper, which like all lithium batteries has a full resting voltage of ~13.5V. So my blue seas ACR never switches off. I need an battery isolator where I can set the connect voltage somewhere near 14.2V, and the isolate at 13.7V or so. Ideally I would like to be able to program each side of the isolator differently, but that may be asking too much. It seems that even many of the adjustable options don't go this high.

I don't think the MOSFET based LVDs (samlex and the latvian one) would work as they are likely one way devices (the body diode allows current to flow from load back to battery, even when off). I am not sure the MErlin/Balmar one will work with lithium batteries as they don't really explain how it works. I may just have to order the Intervolt from oz like you suggested, although I suspect the shipping is going to be brutal - I will find out.
 

DiploStrat

Expedition Leader
Two Easy Answers, One Comment

There are two products that will do what you want:

-- The Magnum Smart Battery Combiner. Note that you need an external solenoid if you want to switch over 25A: http://www.magnum-dimensions.com/smart-battery-combiner

-- The Victron Cyrix-Li-ct :https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf Note that this unit is not adjustable, but is set for lead acid/LiFePO4 combination.

One thought: You may want to use a B2B/DC-DC charger, if only to limit the draw by the LiFePO4 battery. These batteries do not have a rising voltage while under charge can can look a bit like a black hole for amps - you may let all of the smoke out of your alternator, or your wires, if you don't do something to limit the draw.
 

Rando

Explorer
The battery to battery chargers are a good idea, however I would prefer something that is bi-directional. The camper often sits between trips for a couple of weeks or more, so I would like the 240W of solar on the camper roof to also be able to keep the truck battery charged. I will look into the Cyrix-Li-ct some more, I generally have had good luck with Victron equipment and it looks like it should work.

I also limit the charging current to 30A using the BMS and some skinnier wires, so the Magnum may work as is.
 

Rando

Explorer
This could be simple as a cheap PWM on the chassis battery whats manually switched on whenever parked.

This would work, but it seems like a bit of a kludge.

However I think I finally found the answer:
https://www.amazon.com/dp/B071WNSCX5/ref=nav_timeline_asin?_encoding=UTF8&psc=1

Looks to be the same as the Intervolt and is from a US seller. It is programmable over the range of voltages that I need: https://www.jaycar.us/medias/sys_master/images/9003872419870/MB3688-manualMain.pdf

The key was searching for 'programable' as opposed to 'adjustable'. I will report back on how it works - it seems like a pretty good deal if it works as advertised.
 

john61ct

Adventurer
I agree a DCDC B2B like the Sterling range would be ideal.

Put all/any charge source on Starter, or a small cheap lead batt, and the B2B is the only trusted charger that touches the LFP directly.

The LFP bank can be mounted in a Pelican box, DIY Yeti, and used in off grid cabin, on a boat, wherever as needed, recharged from the B2B from any charge source happens to be available.

Note the Balmar MC-214 is a great alt regulator for LFP charging, still useful even with B2B to prevent overloading overheating stock alts or especially modded HO ones.

Charles Sterling has said their 180A B2B will be available RSN
 

john61ct

Adventurer
The battery to battery chargers are a good idea, however I would prefer something that is bi-directional. The camper often sits between trips for a couple of weeks or more, so I would like the 240W of solar on the camper roof to also be able to keep the truck battery charged. I will look into the Cyrix-Li-ct some more, I generally have had good luck with Victron equipment and it looks like it should work.

I also limit the charging current to 30A using the BMS and some skinnier wires, so the Magnum may work as is.
Victron is usually great, but the Cyrix line sucks, not reliable over time.

What is your BMS?
 

Rando

Explorer
It is a super simple board: http://www.batteryspace.com/PCM-with-Equilibrium-function-for-12.8V-LFP-Battery-Pack-30A-limit.aspx
Built around a Seiko controller IC: http://datasheet.sii-ic.com/en/battery_protection/S8254A_E.pdf

So far it has been working very well, it is attached to a 150Ah pack made up of 120 Tenegery 3.2V 5Ah cells.

Also, the LFP batteries are far less picky about charging than lead acid batteries, particularly with a BMS/Protection circuit on the batteries. The only requirements being that you want to get them up to about 14.4 - 14.6V if you want them to be 100% full, and you want to avoid floating above ~13.6V for long periods. Otherwise they don't care about multi stage charging, desulfination, under charging or anything like that. I primarily charge from my solar panels, with the alternator as a bonus if we happen to be driving.
 
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