So I switched from 6v to LifePo4

[twinboat]

Originally Posted by funmoneypit

I would be very interested in seeing a 220ah AGM 6v GC battery for $170. Do you have a link? The ones I bought are certainly not top shelf batteries and I looked all over.

You may not think my comparison is fair and that's fine. My apples to apples comparison is dollars out of my wallet per ah. You may choose different parameters.

I found this at Sams Club. Only 190 AH but $179.00.

Not sure what shelf they are on.

[funmoneypit]

Originally Posted by twinboat

I found this at Sams Club. Only 190 AH but $179.00.

Not sure what shelf they are on.Attachment 324868

Yep, saw that one too. Almost $400 after tax and not 220ah. After you get above 200ah they start to get expensive. Nice try though.

Still would like to see the 220ah agm for $170.

I have been into RC vehicles for 30 years. I have been using LiPo (I am not saying they are the same) batteries since 2007. Many people back then would argue how bad or unsafe the LiPo batteries were. They worked (and still work) great for me.

It's all an individual thing. If you are happy with the LA, you are good then. Others may want something different. Each their own. I am not trying to convince anyone that one is better than the other for their use. I have stated what is better for my use. YMMV

[twinboat]

Originally Posted by funmoneypit

Yep, saw that one too. Almost $400 after tax and not 220ah. After you get above 200ah they start to get expensive. Nice try though.

Still would like to see the 220ah agm for $170.

I have been into RC vehicles for 30 years. I have been using LiPo (I am not saying they are the same) batteries since 2007. Many people back then would argue how bad or unsafe the LiPo batteries were. They worked (and still work) great for me.

It's all an individual thing. If you are happy with the LA, you are good then. Others may want something different. Each their own. I am not trying to convince anyone that one is better than the other for their use. I have stated what is better for my use. YMMV

Question, does your home built lithium battery come with a BMS.

I had an Ebike back in 2010 that had lithium batteries. The BIM failed and I bypassed it. Within a few weeks, the battery pack was swelling so bad that it ripped open the bike bag it was in.

Can't say for shure it was the missing BMS, but it had been fine before then.

[Winemaker2]

I didn't claim they were 220 AH as I knew they were 190. My point is that if you look at $/AH honestly AGMs should come out being attractive for many users.
And I never say hands down they are the best because usage varies and priorities are different.
I still say DIY vs a high end batty isn't an honest comparison. It works for you and that's OK. I would say the largest % of RVers couldn't justify the added cost.

[funmoneypit]

Originally Posted by Winemaker2

I didn't claim they were 220 AH as I knew they were 190. My point is that if you look at $/AH honestly AGMs should come out being attractive for many users.
And I never say hands down they are the best because usage varies and priorities are different.
I still say DIY vs a high end batty isn't an honest comparison. It works for you and that's OK. I would say the largest % of RVers couldn't justify the added cost.

I guess I am a little confused. You say you want to compare apples to apples but then you want to compare the price of a 190ah battery to a 220ah battery. Here are the actual batteries I bought: https://www.batteriesplus.com/productdetails/sligc2agm. Hardly high end. With the 10% discount anyone can get, they were right at $525 after tax. About the best price I could find. There are a lot of higher priced ones out there. To throw out there that I can get a LA battery for $170 (which isn't even correct and after tax is closer to $200) a piece is doing exactly what you claim I was doing, "Most anyone WANTING to justify a position can make the #s work in their favor but to be honest make the analysis apples to apples". The Li batteries I was comparing to are 280ah so better yet. If you want to compare apples to apples, look up the cost of 2-280ah 6v LA batteries. I bet the Li will be less.

You say that LA batteries would be sufficient for most campers and I agree. We are in the Boondocking sub-forum. This isn't a group for most campers.

[funmoneypit]

Originally Posted by twinboat

Question, does your home built lithium battery come with a BMS.

I had an Ebike back in 2010 that had lithium batteries. The BIM failed and I bypassed it. Within a few weeks, the battery pack was swelling so bad that it ripped open the bike bag it was in.

Can't say for shure it was the missing BMS, but it had been fine before then.

Yes, you have to have a BMS. If not, the charger will charge indiscriminately and individual cells will become over-charged leading to swelling. The price comparison I stated in an earlier post does include a BMS. This is a very good point as a BMS is essential when using a Li battery.

[SV K]

Yes, you have to have a BMS. If not, the charger will charge indiscriminately and individual cells will become over-charged leading to swelling. The price comparison I stated in an earlier post does include a BMS. This is a very good point as a BMS is essential when using a Li battery.


Is the above referring to E-Bikes, RC models or RV’s?

Certainly our RV chargers or at least the Magnums and Victrons I have owned do not charge indiscriminately. In 7 years my over-voltage BMS cut-off has never tripped. Nor has it ever been an issue for the other 5 guys coaches we put “homemade” Lifepo4/BMS systems in.

Making your own high amperage BMS is easy and not expensive. A simple volt meter with a programable relay or two is available for around $15. Hook it to a high amp continuous relay/contactor of your choice, program in your desired cut-offs and your battery is protected. I use 4 cell balancers, $25 ea., one for each paralleled string of cells and they are good to go.

If you want to track everything, the Victron 712 with Bluetooth,$200, has a 500amp shunt, is programmable thru your phone or computer and has a relay that you can use a high/low voltage cut/off trigger.

Lots of options for those folks who can’t find what they want available in an off-the shelf BMS.

[astrocamper]

A BMS can also protect from high current load, dead short, prevent charging at a low temperature, too deep of discharge.

[SV K]

A BMS can also protect from high current load, dead short, prevent charging at a low temperature, too deep of discharge.

Absolutely Astrocamper,

I should have mentioned the volt meter solution will take care of the low volt cut-off also.

High current load is achieved in my system via a fuse. Which has never blown. (Although in my case I think one of the Victron gadgets could handle this feature)

Temp control, if desired, would only require a snap disc wired in between the volt meter and the relay/contactor.

I am not in anyway knocking prepackaged batteries or off-the shel BMS's, but sometimes the cost, current limitations, pre-programming or other limitations don't always meet an individuals requirements. Options are a good thing.

My preference would be to be able to purchase an inexpensive programmable BMS that did not include a relay/contactor. Wire to a shunt, wire to a temp sensor(if desired), add relay/contactor, program and enjoy.

[funmoneypit]

Originally Posted by SV K

Yes, you have to have a BMS. If not, the charger will charge indiscriminately and individual cells will become over-charged leading to swelling. The price comparison I stated in an earlier post does include a BMS. This is a very good point as a BMS is essential when using a Li battery.


Is the above referring to E-Bikes, RC models or RV’s?

Certainly our RV chargers or at least the Magnums and Victrons I have owned do not charge indiscriminately. In 7 years my over-voltage BMS cut-off has never tripped. Nor has it ever been an issue for the other 5 guys coaches we put “homemade” Lifepo4/BMS systems in.

Making your own high amperage BMS is easy and not expensive. A simple volt meter with a programable relay or two is available for around $15. Hook it to a high amp continuous relay/contactor of your choice, program in your desired cut-offs and your battery is protected. I use 4 cell balancers, $25 ea., one for each paralleled string of cells and they are good to go.

If you want to track everything, the Victron 712 with Bluetooth,$200, has a 500amp shunt, is programmable thru your phone or computer and has a relay that you can use a high/low voltage cut/off trigger.

Lots of options for those folks who can’t find what they want available in an off-the shelf BMS.

The BMS reference is to any lithium battery. You must have a way to monitor each cell individually.

By indiscriminately charging I mean a 12v charger is just monitoring the overall voltage out of a 12v battery. It does not look at each individual cell. If the cells become out of balance, the battery may still achieve the correct volts to be considered fully charged by the charger but the cells themselves may become unsafe. Without a BMS you can have the exact scenario twinboat described where the cell or cells in the battery swelled. This creates an unsafe battery and the battery should be properly disposed of. This happens all the time in the RC world as some individuals do not monitor each individual cell of a battery pack or do not use the correct charger with a balance port.

[Tombsy]

Originally Posted by funmoneypit

The BMS reference is to any lithium battery. You must have a way to monitor each cell individually.

By indiscriminately charging I mean a 12v charger is just monitoring the overall voltage out of a 12v battery. It does not look at each individual cell. If the cells become out of balance, the battery may still achieve the correct volts to be considered fully charged by the charger but the cells themselves may become unsafe. Without a BMS you can have the exact scenario twinboat described where the cell or cells in the battery swelled. This creates an unsafe battery and the battery should be properly disposed of. This happens all the time in the RC world as some individuals do not monitor each individual cell of a battery pack or do not use the correct charger with a balance port.

I race RC as well, boats now but I probably have 50-60 lipos and a dozen LiFe packs. They all have separate balance plugs to monitor each cell. With the good computer chargers now they won’t charge if a cell’s voltage is too low. Internal resistance of the cells is the best way to monitor a packs health, the values go up as the pack ages. I can discharge my race packs at up to 300 amps in a < 2 minute race.
Most of the puffy batteries I see are from batteries with too low a C discharge rating being over taxed. Another reason is cold packs being discharged at a high rate, a lot of racers use battery warmers to get the temp up to lower the internal resistance.
This is the charger case I built for races, can charge up to 8 packs at once with the 90 amp 24v power supply.

[funmoneypit]

Originally Posted by Tombsy

I race RC as well, boats now but I probably have 50-60 lipos and a dozen LiFe packs. They all have separate balance plugs to monitor each cell. With the good computer chargers now they won’t charge if a cell’s voltage is too low. Internal resistance of the cells is the best way to monitor a packs health, the values go up as the pack ages. I can discharge my race packs at up to 300 amps in a < 2 minute race.
Most of the puffy batteries I see are from batteries with too low a C discharge rating being over taxed. Another reason is cold packs being discharged at a high rate, a lot of racers use battery warmers to get the temp up to lower the internal resistance.
This is the charger case I built for races, can charge up to 8 packs at once with the 90 amp 24v power supply.


Attachment 325075

You are exactly right. Using a good charger AND the balance plug greatly reduces the chance of swelling. As you state, there are other ways a battery can swell.

I have been buying and selling RC's (mostly land based) for 14 years. Most of what I see are novices that don't know what they are doing using the wrong charger or Traxxas batteries. Traxxas 3s lipo batteries swell more than any other battery I see. I believe it is their crappy chargers that don't balance well. They have come out with better chargers in the last couple of years.

Just last week there was a guy on one of our RC groups that was charging a lipo with a non-lipo charger. The thing looked like a small balloon. He's lucky it didn't blow up.

[SV K]

Well I do like to learn and in so doing discovered that Tesla originally monitored/balanced not their individual cells, but their paralleled groups. They did mention that each cell did include a fused link, which I will look into.

After 7 years and 5 friends running coaches with similar set-ups. That being passive balancing, basic hi/low voltage cut-off and a fuse not one has reported any problem of any nature. So I do not agree with the “must” have statement, but agree it would be better to have individual cell monitoring.

Boon-dockers in general, which is where this thread is located, tend to be a bit more experimental than the general rv’ing public and hopefully will gleam from these discussions a variety of solutions for electric storage and select the one best suited to their needs.

[funmoneypit]

Originally Posted by SV K

Well I do like to learn and in so doing discovered that Tesla originally monitored/balanced not their individual cells, but their paralleled groups. They did mention that each cell did include a fused link, which I will look into.

After 7 years and 5 friends running coaches with similar set-ups. That being passive balancing, basic hi/low voltage cut-off and a fuse not one has reported any problem of any nature. So I do not agree with the “must” have statement, but agree it would be better to have individual cell monitoring.

Boon-dockers in general, which is where this thread is located, tend to be a bit more experimental than the general rv’ing public and hopefully will gleam from these discussions a variety of solutions for electric storage and select the one best suited to their needs.

That is great that your system has worked for you. I would suggest you test each cell individually with a volt meter to check how balanced they are. That is the only way to know if your batteries are healthy or not.

I personally will use a BMS which monitors the voltage of each cell for safety and battery longevity. They really aren't that expensive compared to the cost of the batteries.

To learn more, you might want to check out Will Prowse on YouTube. He does a great job of solar charging systems and lithium batteries including the DIY ones.