Addressing the Bottleneck in Stock Alternator Charge Systems

crabbypaddy

Battery to battery chargers are a good idea for a lot of reasons most of which aren't mentioned in that video. Its kind of misleading and sensationalist like most Sterling stuff, the average punter will think you can put 200A from an alternator into a 100Ah battery.

From the manufacturers prespective weedy cables and a 20A fuse may be desirable when the average punter will:

• never check the electrolyte
• never water the battery
• will often excessively discharge the battery
• will often allow sulfation to set in over many months of storage
• will only check/replace the battery when they have murdered it and/or can see/smell/hear a problem with it.

and the battery is stored in a confined space in a vehicle made largely of flammable materials. :pac:

Gibbo SmartGauge http://www.smartgauge.co.uk/rms.html

I'm not promoting Sterling. I do like their products but I don't like their build quality.
I don't think it's sensational to demonstrate how a factory fitment device is designed to run at 10% duty at full load (zero charge if you are powering a fridge). :mad:

Gibbo has some solutions here.

The biggest problems in the system in order of importance are:

• The length and gauge of the wiring to the control box.
• The wholesomeness of the control box.
• The Cabling from the alternator to the starter battery.
• The Cabling from the control box to the domestic battery
• The reduced alternator output regulation to the ΔVoltage of the starter and domestic batteries linked as one asymmetric battery.

Example: Starter battery: 12.8V
Domestic Battery: 12.4V
ΔVoltage batteries linked: 12.6V

The ΔVoltage reduces the alternator current output proportionally to the square of voltage difference. So Instead of the alternator charging a battery of resting voltage 12.4V with 480W it charges a battery of resting voltage 12.6V at 120W. (correct me if I'm wrong here...it's a fog of mathulations, research and empirical findings)

Gibbo SmartGauge http://www.smartgauge.co.uk/rms.html wrote:

Look at the formulae again.......
V=IR and P=VI. Rearrange V=IR to I=V/R and it becomes clear that P=V2/R. Therefore power is proportional to the square of the voltage. So if we double the voltage (ie multiply by 2), the power will be increased by 22 ie by 4 times.
Conversely, if we half the voltage (ie divide by 2) the power will be divided by 22 ie 4.
And this is what we found above when we reduced the voltage from 10 volts to 5 volts. The power reduced from 100 watts to 25 watts.

The Sterling B2B is a unit that caters for all of these issues with ease of install.
I Y from the alternator fit contactors instead on shorter runs, that solves the wiring issues and is pocket friendly. Much how Gibbo recommends but without the smartbank (which is a great unit)
Now if anyone wanted to do it right you'd fit a dedicated alternator that would be cheapest and betterest.




As regards safety margins...it takes me 3 weeks to fully charge my golf cart batteries at 14.8V + temp comp and I water them every 9 months.

Watch out for contaminants in old bottles of distilled. Once they're opened organic matter tends to build flotsam.

crabbypaddy

crabbypaddy wrote: »

the average punter will think you can put 200A from an alternator into a 100Ah battery.

Clicky

crabbypaddy

Sir Liamalot wrote: »

Clicky

I'm not arguing with charger theory or saying that battery to battery chargers don't work. Of course increasing the voltage will increase the accepted current.

A useful video would be one comparing how many more Ah you got in you battery bank with his 40A/80A/120A b2b charger versus a cheap rewire with a heavier cable and a bigger fuse but that wouldn't be half so sensational as implying that you're throwing away 185A from your 14.4V alternator that could be going in your battery full stop.

Yurp, I guessitmate it's 35% cable (possibly more when you consider a B2B will hit current limit sooner). Start there, need more oomph then buy a box. Only reason I'm posting the vid is because it's a video and easy to digest.
Stock systems are rubbish is all I'm aiming to demonstrate.

I'm always a little surprised when you, an engineer, defend the chocolate teapot systems and safety margins. Would it not be favourable to have a rocker switch A: Here be electrons, B: Chocolate teapot power?
Methinks it's simple cost cutting... :rolleyes:

crabbypaddy

Sir Liamalot wrote: »

I'm always a little surprised when you, an engineer, defend the chocolate teapot systems and safety margins. Would it not be favourable to have a rocker switch A: Here be electrons, B: Chocolate teapot power?
Methinks it's simple cost cutting... :rolleyes:

Sterling just gets up my nose, I agree those charging systems are a joke and the sterling battery charger should be a good addition but from the manufacturers point of view they still have to fit a mains charger, distribution unit, control panel. Consider the 15A / 20A alternator charging circuit a very low cost, low complexity, low risk addon to that package. Of course they could fit a complicated microprocessor controlled switchmode charger instead but you don't get something for nothing.

And historically complicated switchmode electronics haven't been very reliable in the recreational market so the manufacturer also has to think about warranty, returns, repairs, replacements, reputation. If they were to offer a b2b charger you can be sure that would be an optional extra costing €600+ just like any other upgrade.

With regards to safety I've been on the receiving end of consumers stupidity. Consumers are great at putting square pegs in round holes. I can guarantee that if manufaturers offered configurable b2b chargers a portion of customers would set a battery boiling charge profile, forget to reconnect the temperature sensor after changing the battery, try to charge shorted batteries connect the output to the input etc. etc. if it can be done it will be done.

I don't believe in warranties, I'd rather they offer the product at a price that hasn't included them. Often it's a gamble that the product will not be returned or driven to it's breaking threshold rather than an assurance of quality..

I get what you are saying and respectfully disagree. Using 2.5mm² cable for a 100A circuit and a 20A relay with 50A written on it is shambolic. Cable is as reliable a solution as they come no excuses.

Would we buy cars than had 100kmph on the speedo but only did 10kmph for safety?

Who else makes battery to battery chargers? CapXon is all I have to say about Sterling.

If you were to look at it objectively and only used the camper in fair weather from a point of view of bang for buck. The same investment in solar on a MorningStar controller (I'd try avoid plumbing through the stock system...too lossy) would have a better return on investment.

In the alternator versus solar panel battle I find the turtle usually wins the race.

crabbypaddy

Sir Liamalot wrote: »

Who else makes battery to battery chargers? CapXon is all I have to say about Sterling.

This is the only one I've seen selling in UK is this one (20A)
https://www.hickleys.com/diagnostics/ctekd250sdual.php

The have an expensive bypass yoke that you can use with that I think is supposed to allow up to 80A pass the charger for the initial bulk charge.

Also found these when I was looking at kayaking trolling motors:
http://www.minnkotamotors.com/Battery-Chargers/On-Board-Chargers/DC-Alternator-Chargers/

Don't know if you can find them this side of the pond but I would say any minn kota dealer should be able to order them in. Also couldn't find out if you can parallel the multibank outputs from their datasheet though so may be limited to 10A. Lastly it looks suspiciously to me like promariner so possibility its sterling anyway.

When I was looking at chargers last year there were lots of options in australia redarc seem to be considered the rolls royce, some have mppt solar charging too. Can remember these two, theres another blue one in a can't remember what it was called.
https://www.redarc.com.au/battery-chargers/in-vehicle-chargers.
http://www.enerdrive.com.au/product/dc-to-dc-battery-charger/


[edit]Just did a google there for blue DC-DC charger its the thunder one:
https://www.batterybusiness.com.au/store/product_detail/C59K

If you scroll down there a couple more I never came across before.

niloc1951

I've One Of These for about ten years. IMHO they are a great piece of kit.
I've 2X110ah house batteries, the originals lasted over eight years and were given a lot of use.
Typical example, the majority of touring is using Aires, often in winter months where the batteries are called on to run the heating continuously over night plus lots of tv and lights. A short run to the next stop brings the batteries back to full charge.

Considering we hear about people getting only two or three years from their batteries the B2B has certainly paid for itself

I can get 35A at the final battery with a cable upgrade spec-ed to 200mV drop at that battery, a low enough state of charge and the right alternator pulley.

I reckon I can get double (x4 according to Gibbo) with double the alternators.

I was thinking earlier a B2B is an MPPT Solar charge controller. I've a 45A one of them sitting idle...hrmmm methinks it's got current limiting....

PV rules the roost March to October. Winter the demand is higher and more difficult to meet.

How hard is the B2B on water Niloc? Don't you have solar as well? I reckon your current battery set might outlast the motor.

When you look at the worst battery you can buy. Car battery; 300 cycles at 50% discharge to 80% rated capacity. I think most batteries die of neglect and poor charging than service. I don't find they deteriorate with age when they are maintained.

niloc1951

I do have to top up the house batteries depending on how much the B2B is in use and yes I do have 200 watts of solar controlled by One Of These

crabbypaddy

Sir Liamalot wrote: »

I was thinking earlier a B2B is an MPPT Solar charge controller. I've a 45A one of them sitting idle...hrmmm methinks it's got current limiting....

Lot of the MPPT's including the morningstar ones can only buck not boost, although if you were feeling adventurous you could knock the alternator voltage up a little http://www.smartgauge.co.uk/alt_mod.html

niloc1951

niloc1951 wrote: »

I do have to top up the house batteries depending on how much the B2B is in use

Outtov interest Niloc what frequency or volume do you replenish?

crabbypaddy wrote: »

Lot of the MPPT's including the morningstar ones can only buck not boost, although if you were feeling adventurous you could knock the alternator voltage up a little http://www.smartgauge.co.uk/alt_mod.html

MorningStar TriStar 45 MPPT Manual wrote:

Conditions That Limit the Effectiveness of MPPT[/B]
The Vmp of a solar module decreases as the temperature of the module increases. In very hot weather, the Vmp may be close or even less than battery voltage. In this situation, there will be very little or no MPPT gain compared to traditional controllers. However, systems with modules of higher nominal voltage than the battery bank will always have an array Vmp greater than battery voltage.

Need more MPPT current anna 24V alternator.

niloc1951

Sir Liamalot wrote: »

Outtov interest Niloc what frequency or volume do you replenish?.

Depends on how much time is spent in hot weather (evaporation) combined with amount of time the B2B is active and when I remember to check them.
On occasions I've added up to a half a litre to each after six months.

Sir Liamalot

Sir Liamalot wrote: »

I can get 35A at the final battery with a cable upgrade spec-ed to 200mV drop at that battery, a low enough state of charge and the right alternator pulley.

Flashed 50A today at 68% SOC (and wrong pulley) :cool: