What VSR (Voltage Sensitive Relay) do I need to install on my yacht?

[coopec43]

Originally Posted by Pete7

Having had a quick look at that article I suggest you bin it or delete it if you have downloaded it, because its nonsense, I quote:

Cars don't try to optimise to keep the cranking battery at 100%; you'll only get about 80% out of it. They simply don't need to, so why should they? A cranking battery will last longer if it's not fully charged,


I suggest you look at something from Sterling Power or Victron. At least shedloads of people have them and can advise if you have a query. Victron come with Bluetooth which is nice.

https://sterling-power.com/

The other option (and cheaper) is a VSR which we used for a decade without any problems, but ideally keep the battery chemistry similar, so either AGM or flooded lead acid.

Pete

Thanks Pete for your helpful advice. (I have binned that article)

I'll stick with Victron as I have just bought a Victron MPPT (Smart) Controller with Bluetooth on advice from the guys on YBW Forum (who have nothing but praise for Victron)

I have just read the helpful comments (following your post) so I have some work to do! Thanks

[more]

Originally Posted by PaulCrawhorn

Current is never "pushed" into any load, including batteries charging.

The source only "offers", makes available up to X amps.

The load is in control of the current drawn.

A DCDC is required for LFP banks, because they try to pull an unhealthy high current

but a good alt VR that limits current can eliminate that need.

The other reason to go DCDC is to get a better charge profile than what the VR puts out, but that need is relative to the data sheet specs for the target battery.

thru and wrong.

alternator limited voltage 14-15 V depend
your lifebatery must be on 10-11V tu pull high current. for current, you must have different voltage. you can charge for example 13V lithium battery ( almost empty) with 13V source 1 billion amps alternator

now i typing on a 12v PC on grid with close to couple million mw amper grid you are right,but if i buy 400v PC he don't start up. because different voltage is negative and current don't flow.

https://www.youtube.com/watch?v=w82aSjLuD_8

[PaulCrawhorn]

I don't understand any of what you wrote.

I was discussing current only, and stand by what I wrote. Of course the CV setpoint of the charge source needs to be correct for the battery as per specs on the data sheet.

The battery will pull less current as its SoC rises, the circuit V rises, and especially once Absorb stage is reached once circuit V = that CV setpoint.

With lead banks it is important to get to 100% as per endAmps spec is reached

IOW hold that CV stage until after the bank is drawing a very low C-rate, say 0.005C but depends on model. This can take 5-6 hours after CC/Bulk stage is complete.

Deka / EPM gives an alternative spec:

> Absorption / CV stage End Point = Current change over 1 hour period of less than 0.1A

Which is great to use after the bank has worn so much the endAmps spec is "never" met.

For LFP you should terminate charge much earlier, in fact assuming balancing is not required, no CV stage is required at all, just charge until circuit hits the setpoint and stop.

[Pete7]

Originally Posted by PaulCrawhorn

I don't understand any of what you wrote.

I was discussing current only, and stand by what I wrote. Of course the CV setpoint of the charge source needs to be correct for the battery as per specs on the data sheet.

The battery will pull less current as its SoC rises, the circuit V rises, and especially once Absorb stage is reached once circuit V = that CV setpoint.

With lead banks it is important to get to 100% as per end Amps spec is reached

I also had a problem understanding, but willing to make an allowance as he is probably posting in a second language rather than his native language.

However, I complete agree with you and if you watch a battery monitor for any time you can see the current drop down as the battery is being charged. Indeed the problem is when you approach 90% you are probably down to single figures for current and if charging via an ordinary alternator, in for a long wait. Been there and now use solar as the main charging source, still takes a while if using lead-acid but at least you're not listening to a diesel engine for hour after hour

Pete

[Bycrick]

It’s really simple: a LA battery is fully charged when it won’t charge anymore at the recommended charge voltage. How can you tell it won’t charge anymore? Either the specific gravity stops going up, or the charge current won’t go down. Anything else isn’t "fully charged."

I’m probably in a minority, but I would have a VSR on the boat. If I want to charge one battery system from another, I’d use a DCDC charger that can base the secondary battery charge only on the condition of the secondary battery.

[Bycrick]

Darned spell checker. Would NOT have a VSR.

[coopec43]

Originally Posted by Bycrick

It’s really simple: a LA battery is fully charged when it won’t charge anymore at the recommended charge voltage. How can you tell it won’t charge anymore? Either the specific gravity stops going up, or the charge current won’t go down. Anything else isn’t "fully charged."

I’m probably in a minority, but I would have a VSR on the boat. If I want to charge one battery system from another, I’d use a DCDC charger that can base the secondary battery charge only on the condition of the secondary battery.

If for some reason the starting battery was "flat" why wouldn't I use a heavy set of jumper leads from the house bank rather than a DCDC charger?

[Bycrick]

In the case of a starter battery being "flat," ie dead, why would one want to connect it across a good battery for starting? So I’d disconnect the dead battery first.

For normal charging, I don’t like the idea of connecting different batteries at different states of charge in parallel and just hoping that everything works out.

[coopec43]

Originally Posted by Bycrick

In the case of a starter battery being "flat," ie dead, why would one want to connect it across a good battery for starting? So I’d disconnect the dead battery first.

For normal charging, I don’t like the idea of connecting different batteries at different states of charge in parallel and just hoping that everything works out.

Yes by-pass the flat battery and take the leads to the starter.

Doesn't the VSR (VOLTAGE SENSITIVE RELAY) take care of "different batteries at different states of charge in parallel"?

[more]

Originally Posted by Pete7

I also had a problem understanding, but willing to make an allowance as he is probably posting in a second language rather than his native language.

However, I complete agree with you and if you watch a battery monitor for any time you can see the current drop down as the battery is being charged. Indeed the problem is when you approach 90% you are probably down to single figures for current and if charging via an ordinary alternator, in for a long wait. Been there and now use solar as the main charging source, still takes a while if using lead-acid but at least you're not listening to a diesel engine for hour after hour

Pete

alternator is CV charger set 14V
almost empty lithium battery is 13V
what is difference in voltage from source to battery.

[PaulCrawhorn]

Yes if the FF source C-rate is high, say over 0.3C then you can get to 95% in under two hours

but very bad for bank longevity to stop anywhere but 100%

and that may take more than five more hours.

The ideal is to do that Bulk /CC stage quickly in the early morning via FF source

then use your solar to finish the job get to 100% Full.

Ideally every cycle, but at least a few times a week.

Since a say 400Ah bank might be drawing only 10-20A for the last 4-5 hours it does not take a lot of panels...

[moseriw]

Originally Posted by PaulCrawhorn
Current is never "pushed" into any load, including batteries charging.


OK, am I missing something? Why is it common to charge FLA's at max 20 - 25% of capacity if it is useless as the battery decides what it is drawing? Yes of course batteries takes what they need if they are connected together which is a problem as one has ongoing charging/dischargingbetween the units.

So why b uy a 100A charger when the battery says " Oh you want me being fully charged within two hours but I decide to take 10 hrs for it?"

[PaulCrawhorn]

Originally Posted by moseriw

Why is it common to charge FLA's at max 20 - 25% of capacity if it is useless as the battery decides what it is drawing?

FLA will not be able to draw that much for long, out of all the lead chemistries they are the most limited.

But overall time is still going to be about the same as higher CAR units, because as SoC rises, the current rate drops so drastically, especially during the last 4-6 hours.

> Yes of course batteries takes what they need if they are connected together which is a problem as one has ongoing charging/discharging between the units.

None if that makes any sense, that last part is not a thing in a properly designed system. "Batteries take what they need" no matter what, lead ones anyway. More accurately, lead banks take what they take, cannot take at too high a rate, and offering higher current than that rate has no effect.

Making 300A available has almost zero impact on charging time for a normal lead bank under say 1000Ah, compared to a 200A source.

> So why buy a 100A charger when the battery says " Oh you want me being fully charged within two hours but I decide to take 10 hrs for it?

Well high C-rates in Bulk stage are essential for AGM longevity, try to get up to 6C if you can afford it.

But yes for FLA, 100A charger would only be helpful for a bank over 400Ah in size.

However a good charger are "infrastructure", will last longer than the batteries, which are consumables

so buying one that will handle your future upgrades in coming decades, is a pretty good idea, custom user profile adjustments in particular for changes in chemistry, upgrading to LFP with its ability to get back to full in 2 hours...

No lead bank can get back to 100% Full from 50% DoD in under 5-6 hours, no matter what.

[moseriw]

PaulCrawhorn Paul, thank you for your input. I am fooling around with charging for at least 8 years and your comment did it. Looks like there is no way to upgrade the bank to modern technology. My Trojans are 2 years old but the next ones will be the oncoming Sodium-Ion Batteries ( https://www.bluesky-energy.eu/en/saltwater_battery/) as I do not want to support LiFePo4.

[PaulCrawhorn]

LTO is a great chemistry, much longer lived, higher CAR (full in 15min) can go dead flat no problem.

Just not so energy dense.