Replacing batteries

[ullar]

Originally Posted by d design

I find Lead acid more complicated IMHO

Lead acids are Plug and Play, Lithiums, at least more affordable ones, are not.

I've nothing against a nice set of LFePO4-s. Also, my boat has pretty advanced alternator and mains chargers, so is more or less ready for Lithiums. I just chose the most cost efficient way -- deep-cycle open lead acids.

[Maine Sail]

Originally Posted by d design

Ok then. A simple monitor and relays for low voltage cut and high voltage cut can be used. Lead acid batteries should also have this system. How that fancy name BMS comes here I do not know. Maybe BMS should stand for Balancing management system instead :0

Except that any cuts should be done based on cell level voltages not pack level.. A simple BMS such as the House Power BMS costs about $150.00, pretty cheap insurance..

[ullar]

Originally Posted by Maine Sail

Except that any cuts should be done based on cell level voltages not pack level.. A simple BMS such as the House Power BMS costs about $150.00, pretty cheap insurance..

Isn't that called balancing? You charge until all cells are full and without overcharging any of them.

[Pete7]

LfePO4s are not going to happen, nor probably are AGMs. Th OP has 3 x 145 AH batteries that have lasted 4 years and only failed due to a charging problem.

If the bank has to be replaced then UK prices will be £300 (500 USD) for 3 x Varta FLAs or £950 (1600 USD) for 3 x Lifeline AGMs. You can buy a lot of other stuff for $1000.

Pete

[goboatingnow]

If the bank has to be replaced then UK prices will be £300 (500 USD) for 3 x Varta FLAs or £950 (1600 USD) for 3 x Lifeline AGMs. You can buy a lot of other stuff fo

absolutly, buy the Vartas, go sailing, everything else is a distraction.

dave

[sailorboy1]

we spend way too much time worrying about batteries that in the big picture of boating are low cost (unless you are using expensive batteries without the needed support systems and killing them early, in which case you should learn the errors of your ways and get cheaper one)

[Maine Sail]

Originally Posted by ullar

Isn't that called balancing? You charge until all cells are full and without overcharging any of them.

No, not at all. The HP BMS does HVC at 14.2V. This means all my charge sources are physically disconnected/relays broken at 14.2V. These are considered "warning level" protections.

Cell balancing does not even begin until you have manually disabled HVC and then manually pushed the voltage to cell balancing range. Balancing does not occur until 3.7VPC/14.8V.

If I ever do need to cell balance I use a bench-top power supply with the bare minimum current to push to balancing voltage range. I consider cell balancing of Li not much different than a proper equalization practice for flooded batts. This means the event is physically monitored and done with the bare minimum current necessary and nothing more.

With the HP BMS cell balancing occurs well after HVC so it can be done manually, safely and with the lowest possible current. This is the SAFE way to incorporate cell balancing into a BMS.

It is physically impossible with the HP BMS, if you wire it correctly, to hit balancing levels unless HVC is manually disconnected and overridden. If you wire it like a buffoon you will hit balancing levels and this can or could be potentially dangerous with a massive current source behind it.

Wire it and use it correctly and it is as safe as drinking a glass of water...

[Maine Sail]

Originally Posted by Pete7

LfePO4s are not going to happen, nor probably are AGMs. Th OP has 3 x 145 AH batteries that have lasted 4 years and only failed due to a charging problem.

If the bank has to be replaced then UK prices will be £300 (500 USD) for 3 x Varta FLAs or £950 (1600 USD) for 3 x Lifeline AGMs. You can buy a lot of other stuff for $1000.

Pete

Bingo... ! Sorry for the side track but it seems some want to distract with Li discussions and those points should be addressed when they are unclear or misleading.....

[d design]

I use lifepo4 and lipo in rc planes and boats. The performance is mind blowing. I have A lipo that can accept a charge of 8C and a discharge of 70C. Thats like a supercapacitor! Energy density of these things is mind blowing compared to LA. I have a few Lipos that i have put atleast 4000 cycles on them and they still have amazing performance. Thats what motivates me. Its the future. Time to move forward. Get rid of Hunks of lead.

[Maine Sail]

Originally Posted by d design

I use lifepo4 and lipo in rc planes and boats. The performance is mind blowing. I have A lipo that can accept a charge of 8C and a discharge of 70C. Thats like a supercapacitor! Energy density of these things is mind blowing compared to LA. I have a few Lipos that i have put atleast 4000 cycles on them and they still have amazing performance. Thats what motivates me. Its the future. Time to move forward. Get rid of Hunks of lead.

LiFePO4 is nowhere near that type of Li battery, and safer too, but still a heck of a LOT better than lead on cycle life and current acceptance.

[Pete7]

Originally Posted by d design

I use lifepo4 and lipo in rc planes and boats. The performance is mind blowing. I have A lipo that can accept a charge of 8C and a discharge of 70C. Thats like a supercapacitor! Energy density of these things is mind blowing compared to LA. I have a few Lipos that i have put atleast 4000 cycles on them and they still have amazing performance. Thats what motivates me. Its the future. Time to move forward. Get rid of Hunks of lead.

and how much are these super dupper batteries if you needed to buy one tomorrow for your yacht, say the equivalent of a 110 AH 12v battery?

What is wrong with lead? how does 60kgs of batteries affect my 5100kg yacht?

Pete

[sailr69]

Originally Posted by ullar

I actually prefer acid draining to bilge from where it's quick task to pump out with manual bilge pump. Lots of flushing to do afterwards of course. And sodium bicarbonate (baking powder) helps a lot. Have thought about it but still would not like to live through it.

My battery box has drain holes.

for 22 years and using T145 Trojans, I cannot see any reason for acid leaking from the batteries. unless, the cases crack, boat turtles or maybe leaving the caps off. ???

[sailr69]

Originally Posted by Pete7

LfePO4s are not going to happen, nor probably are AGMs. Th OP has 3 x 145 AH batteries that have lasted 4 years and only failed due to a charging problem.

If the bank has to be replaced then UK prices will be £300 (500 USD) for 3 x Varta FLAs or £950 (1600 USD) for 3 x Lifeline AGMs. You can buy a lot of other stuff for $1000.

Pete

I have used Trojans T105"s for a period of 10+ years. replaced them with T145"s never had a issue with them. It does help to contact Trojan with advice though. house batteries are six 6 volts. been using a battery monitor and smart regulator.

[d design]

You get what you pay for. Lifepo4s cost more because they are many times better than lead

[mrm]

Originally Posted by Pete7

and how much are these super dupper batteries if you needed to buy one tomorrow for your yacht, say the equivalent of a 110 AH 12v battery?

What is wrong with lead? how does 60kgs of batteries affect my 5100kg yacht?

Pete

I think you wrote it with a tongue in cheek but I'll try to answer anyway. There are three main advantages to LiFePO4:

1. charge acceptance (max. current ('bulk' if you like) almost till the end),
2. safe depth of (dis)charge range: 95% <-> 20%,
3. lifetime measured in thousands of cycles,
4. very flat discharge curve (almost no voltage sag).

For some, also low weight, no acid to spill and a very low self discharge is a factor.


There are some negatives as well:

1. LiFePO4's really shouldn't be charged below 0 deg. Celsius,
2. they are much less forgiving to overdischarge and overcharge, so some monitoring and protection circuits are necessary,
3. end of charge voltage differs some from Lead tech., some tweaking of charge sources is necessary,
4. state of discharge is very difficult to estimate by voltage measurement. Best is to have Ah / Wh counter.

Lead is best in ballast, though.