Battery to battery charger views?

[j04n]

Hi All,

 

Been reading about alternators only charging batteries up to 80% and very slowly at that, which I have seen for myself on my MICC. The fix seems to be to install a battery to battery charger in order to achieve 100% charge, 5 times quicker. That's the theory at least anyway. Apart from them being pricey I would appreciate any practical advise on whether you feel the benefits are real, worth it and if there are any draw backs? Alternator early failure for example. Thanks in advance.

[cuthound]

It is the battery itself which limits the charging current, not the alternator or anything else used to charge it.

 

Also alternators, or anything else used to charge the battery will eventually get it up to 100% charge providing the charger can output around 14.4 volts or more.

 

Anything that claims to charge a battery to 100% five times quicker is just marketing bollux, I'm afraid.

 

Whatever charging system is used, providing its output is enough to charge the battery, will charge up to 80% fairly quickly, and then take 4-8 hours to put in the last 20%.

 

The only two things I ever saw that reduced charge times for wet lead acid batteries, were:

 

1 - a compressed air blower in a submarine, which shook up the electrolyte. Necessary to reduce the vulnerability of a diesel-electric sub, when sitting on the surface charging it's batteries, and,

 

2 - a battery with transistor operated shunts fitted to each cell, so that the cells that charged first were bypassed allowing the charge current to only go to the cells which needed it. (Not sure if this actually reduced charge times, but it certainly prolonged the life of the first cells to charge).

 

Edited to correct the quaintly named auto-correct.

Edited October 11, 2016 by cuthound

[Tony Brooks]

Its not quiet as clear cut as Cuthound implies although I tend to agree with him on the whole.

 

Such devices will boost the charging voltage and in that way force more "amps" into the battery at any given state of charge. However how many of those amps are actually charging , how many are producing heat, and how many are turning the water into the electrolyte into gas is anyone's guess.

 

Depending upon your alternator you can boost the charging voltage by putting a diode in the sense wire that may be inside or outside the alternator. This costs pence and a little time. If you do not fancy that then you could fit an Adverc (my choice) or a Sterling PDAR advanced controller. All will boost the charging voltage and stuff more amps into the battery (other controllers are available). They will not suffer efficiency losses of the electronics in the B to B and A to B controllers. The normal advanced controllers are easy to take out of use for diagnostic purposes by disconnecting one wire where as the A to B is not so easy. The B to B probably in effect diverts engine alternator charge to the domestic bank but without boosting the voltage it will make very little difference to charge times (maybe half an hour or so). A similar effect at less cost can be produced by fitting a voltage sensitive split charge relay but you may need a switch in the coil feed to turn if off if the domestic (larger) alternator shut down before the engine one.

 

The alternators SHOULD self limit for current to safe levels but in hot engine rooms may not as they may not if the design is poor. I would suggest there is a greater danger of reduced battery life.

Edited October 11, 2016 by Tony Brooks

[nicknorman]

There is a theory, probably true, that increasing the voltage and hence current can increase charge times. More current goes to gassing and the bubbles act as a barrier between plates and electrolyte.

[j04n]

thanks very much All. You've saved me £350 ish! much appreciated.

[Chewbacka]

Spend the £350 saved on a couple of solar panels and a controller, that way in the summer months you will get to 100%

[WotEver]

There is a theory, probably true, that increasing the voltage and hence current can increase charge times. More current goes to gassing and the bubbles act as a barrier between plates and electrolyte.

Mr Gibbo said (and therefore I believe it) that the above was so.

 

Note that (given long enough) 13.6V is quite sufficient to charge a battery to 100% and the battery will thank you for treating it so gently.

 

Tony

[dor]

Check what voltage your alternator charges at. Even recent ones might only go up to 14.0V. There is a good chance you can find a replacement regulator on eBay for £10 - £15 that will increase the charging voltage. E.G. on my Vetus (Iskra) alternator the regulator was set at 14.0V. I have replaced it with one at 14.4V and 14.6V and 14.8V ones are available. 14.8V not recommended for sealed batteries.

[Tony Brooks]

 

Check what voltage your alternator charges at. Even recent ones might only go up to 14.0V. There is a good chance you can find a replacement regulator on eBay for £10 - £15 that will increase the charging voltage. E.G. on my Vetus (Iskra) alternator the regulator was set at 14.0V. I have replaced it with one at 14.4V and 14.6V and 14.8V ones are available. 14.8V not recommended for sealed batteries.

 

 

Nor for open cells unless you check and top up as required regularly. I think a major mariniser ended up buying new batteries for a customer because of this.

 

[Arthur Brown]

Batteries in permanent float as in a data centre UPS battery room sit at a permanent charge to a precisely specified (maybe to three decimal places ) voltage given by the maker around 13.2v but this is when they are held on true float. They usually get a reliable life of 10 years so they must be doing something right! (or three full discharges!) .

 

At other than float a higher voltage is used to increase the charge rate, BUT this then becomes a cyclic charge regime with the attendant need for regular electrolyte level check and top up. Long periods at 14+ volts is no good for a fully charged battery.

[Saffa]

I put new Trojan 12 v batteries in and the data sheet asks for 14.82 v on Bulk Charge. My Leece Nevel alternator only used the charge qt 14,2v. I have now installed the sterling Universal Advanced Digital Alternator Regulator Pro Reg DW (waterproof) PDARW. I now get a bulk charge voltage of 14.79. I do check the batteries water levels regularly but dont seem to top up much.

 

I would say charging times have reduced slightly on the bulk side but the Sterling Regulator calculates this time upon the start of each charge then goes into float mode so effectively lets the inbuilt regulator take over for the last bit.

[j04n]

mine charge around 14.2V. I am interested in any gains because I am hoping to CC for 3 months but only intend cruising for 3 to 5 hours every other day or even moor up for 2 to 3 days on occasions but suspect I will not be putting enough back into my domestic batteries without going without lights(figure of speech) for sometime or running my engine whilst moored. Or live on jam and bread! ?

[WotEver]

I suspect that for ordinary leisure batteries (as opposed to traction batteries), you won't gain much by charging a couple of points higher and would eventually shorten the battery life somewhat. Sure, 14.4V would be better but a 1.5% increase in voltage wouldn't make s huge difference.

 

What method do you use to determine the SoC of your bank?

 

Tony

[j04n]

I suspect that for ordinary leisure batteries (as opposed to traction batteries), you won't gain much by charging a couple of points higher and would eventually shorten the battery life somewhat. Sure, 14.4V would be better but a 1.5% increase in voltage wouldn't make s huge difference.

What method do you use to determine the SoC of your bank?

Tony

I have a MICC but because the % charge goes out of sync I usually leave it on mains charge for several days before resetting the MICC. Of course off grid I won't be able to do that so will have to monitor the amps being put back into the battery as well as the voltage. Edited October 11, 2016 by j04n

[Theo]

Mr Gibbo said (and therefore I believe it) that the above was so.

 

Note that (given long enough) 13.6V is quite sufficient to charge a battery to 100% and the battery will thank you for treating it so gently.

 

Tony

 

I have found the Adverc successful. It increased the field current to produce much higher charging currents at low states of charge. Once the batteries reached 80% soc then it's cunning control system gives a period of time at 14.4V (just above gassing) followed by a period at 13.9V (just below gassing). This is supposed to give the most rapid charging while being kind to the batteries.

 

I have a 90A alternator and without the Adverc it would be producing IIRC only 30A by the time the charging voltage had increased to 13.7V with the Adverc the initial current was in the region of 70A as long as I ran the engine fast enough.

 

N

[Theo]

mine charge around 14.2V. I am interested in any gains because I am hoping to CC for 3 months but only intend cruising for 3 to 5 hours every other day or even moor up for 2 to 3 days on occasions but suspect I will not be putting enough back into my domestic batteries without going without lights(figure of speech) for sometime or running my engine whilst moored. Or live on jam and bread!

 

Sounds similar to our cruising pattern. It is necessary to bring the charge up to 100% from time to time. I ensure that it reaches this at least once a week. I can only do this by running the generator from time to time, even with 240Wp solar panels. For the rest of the week I tend to run with a minimum of 75% in the morning before I start the engine to a max of 92% when I stop for the day. That's without the 3 day stop. With a three day stop I will be running down close to 50%. I have 720Ah nominal capacity.

 

N

[MtB]

I have a MICC

 

 

What is an MICC?

[dor]

 

 

What is an MICC?

Don't think it is mineral insulated copper clad cable, or Manchester International School of Christ!

 

Try this one: http://www.mastervolt.com/products/battery-monitoring-panels/masterlink-micc/

[j04n]

 

I ensure that it reaches this at least once a week.

That was my main concern for good battery health as I didnt think running on partial charge for 3 months would do them any good.

[Tony Brooks]

That is what we have tended to do over the last few summers, but we have a small (60W) solar panel and we leave the boat for a few days with everything turned off while we return home. The solar seems to bring the batteries to fully charged over three days or so in the summer and our battery life has increased since fitting it. The advice to spend the money on solar seems good as long as you are CCing in the summer. However I question if its sensible to tie up for those periods without a larger solar input and possibly more engine running.

[WotEver]

 

I have found the Adverc successful. It increased the field current to produce much higher charging currents at low states of charge. Once the batteries reached 80% soc then it's cunning control system gives a period of time at 14.4V (just above gassing) followed by a period at 13.9V (just below gassing). This is supposed to give the most rapid charging while being kind to the batteries.

 

I have a 90A alternator and without the Adverc it would be producing IIRC only 30A by the time the charging voltage had increased to 13.7V with the Adverc the initial current was in the region of 70A as long as I ran the engine fast enough.

 

N

Yeah but... have you noted how much time that actually saves? It'll undoubtedly save some time whilst the batteries are in bulk but how much? 30 minutes?

 

Tony

[j04n]

I question if its sensible to tie up for those periods without a larger solar input and possibly more engine running.

I'm going to be cruising in the winter so I can forget solar. More engine running and cooking on travel power whilst engine running I guess....... oh and lots of jam and bread! ..... oh and planned marina stop overs with electrical hook up.

Edited October 12, 2016 by j04n

[nicknorman]

What is an MICC?

It's a Mastervolt remote control panel for their range of Combis etc and includes a shunt so it's also an AH-counting battery gauge.

[cuthound]

Batteries in permanent float as in a data centre UPS battery room sit at a permanent charge to a precisely specified (maybe to three decimal places ) voltage given by the maker around 13.2v but this is when they are held on true float. They usually get a reliable life of 10 years so they must be doing something right! (or three full discharges!) .

 

At other than float a higher voltage is used to increase the charge rate, BUT this then becomes a cyclic charge regime with the attendant need for regular electrolyte level check and top up. Long periods at 14+ volts is no good for a fully charged battery.

For data centre and telecommunications applications, where the batteries are only discharged in the event of a power failure, hopefully only for 30 seconds or so whilst the standby generators start up, flooded lead acid batteries are usually floated between 2.23 and 2.27 volts per cell (at 25°C, corrected for other temperatures).

 

In the same situation Valve Regulated Sealed Lead Acid batteries are usually floated between 2.25 and 2.3 volts per cell, as the calcium content of the plates allows a higher float voltage. However the use of pure lead acid VRSLA's is becoming more common, as they last longer, by eliminating plate failure due to group bar corrosion caused by a reaction between the land/calcium alloy of the plate and the pure lead group bar.

 

Edited to remove a letter "c", masquerading as a space.

Edited October 12, 2016 by cuthound

[Theo]

Yeah but... have you noted how much time that actually saves? It'll undoubtedly save some time whilst the batteries are in bulk but how much? 30 minutes?

 

Tony

 

It's not a lot, I am sure. I have a swankey Sterling charger and an undersized gennie. The gennie won't work with the charger on 50A so I reduce the output to approx 40A (75%). It's not long (30 mins or so if I start charging at 60% soc on the Smartgauge) before the current drops below the 40A showing that at this point the charger is producing as much as it would if it were set at 100%.

 

Getting back more closely to the point. The Adverc does lift the charging rate which is good but how good is debatable and does the battery care thing as well. Again is this necessary and is it worth the £200 or so that I paid for it? I've got it now and it does what it says on the tin.

 

Nick