LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[Jd1]

Originally Posted by rfadler

Why are you bothered that everything hinges on the disconnect with the lithiums? Would you feel better if you had a BMS (such as the HPBMS) that was configured as a backup?

My understanding is that in a traditional LiFePO4 installation (if there is such a thing) a disconnect is a safety device if other things fail because disconnecting will most likely destroy the alternator. In Rolf's installation the LA battery is there to absorb the spike and protects the alternator.

Am I missing another reason that you would not want to use the disconnect as described by Rolf? It seems like a very elegant solution.

You are correct in that the disconnect is a safety device (and if done properly will not destroy the alternator). The problem in this case is that the disconnect is not a safety backup but the primary means of ending charging and there is no safety backup.
Under 'normal' circumstances the charging source would not exceed total pack allowable voltage and the disconnect happens when something is broken.

Having said all that, I think I will be happy with a double disconnect. Now I have to find very reliable voltage controlled relays (or control modules to activate relays).

[Jman]

Originally Posted by Jd1

Turns out that yes, I had heard of them before but it had totally dropped out of my mind (old age is a terrible thing). Googling on this type of charger revealed plenty but none seem to include a litium charging profile or are adjustable. I thought I had hit the jackpot with Sterling but reading the manual showed that there was no lithium profile .... and I would really require something where I can adjust the charge voltage. It can be a real dumb box because it only needs a constant voltage output and no multi stage wizardry.
I will continue looking for that kind of a charger as that is exactly what I need.

Jens

Please advise if you find one, or if anybody else know of one.


Sent from my iPad using Cruisers Sailing Forum

[roetter]

Originally Posted by Jd1

You are correct in that the disconnect is a safety device (and if done properly will not destroy the alternator). The problem in this case is that the disconnect is not a safety backup but the primary means of ending charging and there is no safety backup.
Under 'normal' circumstances the charging source would not exceed total pack allowable voltage and the disconnect happens when something is broken.

Having said all that, I think I will be happy with a double disconnect. Now I have to find very reliable voltage controlled relays (or control modules to activate relays).

This is the only programmable voltmeter I could find and I am using it on three boats.
Programmable 4 Digit Red LED AC/DC Volt Meter with dual control. Good for HHO System

By the way - my solar and shore power are set to LiFePo charging parameters. The solenoid cuts out only for the alternator.. You could hook up a MC-614 to the alternators and program it to LiFePo, but then your LA batteries never get full. When the alternator charges I am always on board and as a backup I have a loud alarm hooked up to the Junsi.

[Maine Sail]

Originally Posted by roetter

You could hook up a MC-614 to the alternators and program it to LiFePo, but then your LA batteries never get full. When the alternator charges I am always on board and as a backup I have a loud alarm hooked up to the Junsi.

I use an AGM as a reserve battery. It gets the same profile as the LFP when I want it to. Every now and then I hit it with 14.4V for a bit and all is good. The idea of keeping an LA battery on-board for starting or other purposes is, IMHO, made obsolete by LFP..

Our LFP bank is an everything bank and the AGM is there simply as an emergency redundant back up battery.. I capacity test this AGM yearly and so far with no use and "floating", when the LFP is charging or when I engage it, has shown only about a 2Ah change over 3 years of ownership. I really can't complain about that....

Keep in mind this battery is almost always at 100% SOC with resting voltages usually in excess of 12.87V so pushing it back to absorption is not required every day. The self discharge on this battery with the cold waters in Maine is next to nil...

It should be noted that this AGM was cycled and broken in before I commissioned it and Ah capacity was determined to be approx 1Ah less than the factory rating (not unusual). Ideally I would have chosen a GEL as my back up (14.1V) is a lot closer to LFP, but I had the AGM kicking around. When I want to charge it a bit I simply hit the parallel switch when the LFP is as 13.9V. It gets an absorption level about once per month via solar, if I remember.....

[Jd1]

Originally Posted by roetter

This is the only programmable voltmeter I could find and I am using it on three boats.
Programmable 4 Digit Red LED AC/DC Volt Meter with dual control. Good for HHO System

By the way - my solar and shore power are set to LiFePo charging parameters. The solenoid cuts out only for the alternator.. You could hook up a MC-614 to the alternators and program it to LiFePo, but then your LA batteries never get full. When the alternator charges I am always on board and as a backup I have a loud alarm hooked up to the Junsi.

Thanks for the link to the volt meter!
I do have an MC614 but as you said, I didn't think it would keep the LA in good shape if I set it to LiFePo parameters. Some more pondering is required .....

[Maine Sail]

Originally Posted by Jd1

Thanks for the link to the volt meter!
I do have an MC614 but as you said, I didn't think it would keep the LA in good shape if I set it to LiFePo parameters. Some more pondering is required .....

Why are you worried about the LA batt at all? Use a low self discharge battery like a GEL or AGM stick it on-board fully charged and "float it" every now and then at LFP levels..

If you really feel the need get a small solar panel to feed it but I have found zero need to worry about my AGM with LFP. It's there, and will service my needs if it has to. No need to over think it...

[evm1024]

Just finished up top balancing 4) 700AH Winston cells. They came:

3.503
3.497
3.482
3.513

They have been sitting paralleled after bringing them up to 3.75. Then just got done taking them to 3.800.

Time to think more seriously about the rewire and reprogram the MC-612 and inverter/charger.

The general plan is to use the HousePower BMS monitoring, alarms and over/under disconnect. Alternator charging controlled with the program and the inverter charger used to charge under manual supervision and then shut off.

Nothing is cast in stone yet.

I do go back and forth between getting an AGM starting battery. I do have a windlass battery that forms the backup start battery so a dedicated start battery is really not needed.

Regards

PS balqon shipped these cells out within a week and I was able to get a 14% discount....

It took weeks to read this entire thread but is worth it.

[Jd1]

Originally Posted by evm1024

PS balqon shipped these cells out within a week and I was able to get a 14% discount....

How did you manage the discount and how did you get them shipped out so quickly ????

I just did the math on that .... you got them for $600 each ??? WOW !

[evm1024]

Originally Posted by Jd1

How did you manage the discount and how did you get them shipped out so quickly ????

I used their chat and spoke with one of their reps. I was looking for a discount and asked for it. A lessor discount was offered but that did not make me want to buy.

Once the deal was agreed on I kept in contact with the person handling the credit card info. Asking for a ship date. The 700 AH are listed as being in stock.

Perhaps it was luck.

I'm in Portland, Not that far from Victoria - an easy drive....

[Jd1]

Originally Posted by evm1024

I'm in Portland, Not that far from Victoria - an easy drive....

How where they shipped to you and what did shipping cost ? I ship most of my freight through Blaine to get to Victoria because it makes a large difference in cost compared to shipping to Victoria directly. I would think it would cost me the same amount for freight to Blaine.

[evm1024]

Originally Posted by Jd1

How where they shipped to you and what did shipping cost ? I ship most of my freight through Blaine to get to Victoria because it makes a large difference in cost compared to shipping to Victoria directly. I would think it would cost me the same amount for freight to Blaine.

By truck for $150.

[Jd1]

Well that was an easy way of spending about $3k by the time it's here
4 cells, 700 Ahr each, $600 each, $150 freight (partial, to it's first stop), $13 for bolts and interconnects, two week shipping promised (we will see).
I did a LOT of fence sitting for maybe a year or so! Well, it's done now!

Need to decide on BMS and relays.
I am thinking House Power BMS and their fuel gauge but have no idea about relays (they only show a 40 amp relay). Any suggestions ?
I will run three relays, one for the charge bus, one for the load bus (both controlled by the BMS and a 'holy ****' relay powered by a Cellogger8 as a failsafe.

[evm1024]

We are both in the same boat

with my 700 ah set I am also planning to use the housepower BMS for monitoring and alarms. I've got one of the LED voltmeters with voltage triggered relays for disconnects (to start with) but I wonder about the repetability of the trigger points. Inverter/charger set to custom charge voltage (13.8 bulk and abs no float) but plan on turning that on manually. Older Balmar Alt and MC612 reg set as close to MainSails MC614 spec as possible.

The engineer part of me is feeling the pull of designing a monitor/charge controller module badly.

We might come up with a 'standard' 700 AH setup. Who knows?

Congrats!

[evm1024]

I keep going round and round with the paradigm shift that LiFePO4 requires. One thing that I cannot discard is the notion of a second battery that could be used as a backup for starting.

My (soon to be installed) 700 AH house bank has plenty of start capability. Even nearly fully discharged.

Currently I have a house bank, a start battery and a windless battery. The start and house will become LiFePO4 and the windless could remain a LA. I currently have the option of charging the windless battery with an echo charger or with a 10 amp charger powered from 120 VAC.

With a LiFePO4 house battery charging the windless battery off the inverter does not feel as wrong as when the house was LA. Of course the inverter battery becomes the "backup" start battery.

[Ex-Calif]

Originally Posted by evm1024

I keep going round and round with the paradigm shift that LiFePO4 requires. One thing that I cannot discard is the notion of a second battery that could be used as a backup for starting.

My (soon to be installed) 700 AH house bank has plenty of start capability. Even nearly fully discharged.

Currently I have a house bank, a start battery and a windless battery. The start and house will become LiFePO4 and the windless could remain a LA. I currently have the option of charging the windless battery with an echo charger or with a 10 amp charger powered from 120 VAC.

With a LiFePO4 house battery charging the windless battery off the inverter does not feel as wrong as when the house was LA. Of course the inverter battery becomes the "backup" start battery.

What would be wrong with a DC to DC charger for Aux batteries.

I could see a LA for windlass and for starter battery and isolating them from the LiFePO system seems like a good idea.

In fact an AC charger up front for a LA placed up front makes sense as the wire run can be lower gauge.

Where the run is short (start battery) DC to DC avoids the conversion losses.

So maybe both? OTOH (of course) - having a "common" charger model means built in redundancy - i.e. if the windlass battery charger failed one could swap it out with the starter charger.

Hmm... OK depending on the wire run you could also have one charger for both aux batteries.

Wow - just had a whole debate with myself and am still confused...